diff --git a/VERSION b/VERSION
index f9f294c7..ee16f1e6 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-8.3.637
+8.3.638
diff --git a/doc/html/commands.html b/doc/html/commands.html
index d3fd88bf..06bdbc73 100644
--- a/doc/html/commands.html
+++ b/doc/html/commands.html
@@ -334,23 +334,23 @@
 </TR>
 <TR>
 <TD> <A HREF=undo.html> <B>undo</B></A> </TD>
-<TD> <A HREF=units.html> <B>units</B></A> </TD>
 <TD> <A HREF=updatedisplay.html> <B>updatedisplay</B></A> </TD>
+<TD> <A HREF=version.html> <B>version</B></A> </TD>
 </TR>
 <TR>
-<TD> <A HREF=version.html> <B>version</B></A> </TD>
 <TD> <A HREF=view.html> <B>view</B></A> </TD>
 <TD> <A HREF=windowborder.html> <B>windowborder</B></A> </TD>
+<TD> <A HREF=windowcaption.html> <B>windowcaption</B></A> </TD>
 </TR>
 <TR>
-<TD> <A HREF=windowcaption.html> <B>windowcaption</B></A> </TD>
 <TD> <A HREF=windownames.html> <B>windownames</B></A> </TD>
 <TD> <A HREF=windowscrollbars.html> <B>windowscrollbars</B></A> </TD>
+<TD> <A HREF=xview.html> <B>xview</B></A> </TD>
 </TR>
 <TR>
-<TD> <A HREF=xview.html> <B>xview</B></A> </TD>
 <TD> <A HREF=zoom.html> <B>zoom</B></A> </TD>
 <TD> <A HREF=tk_path_name.html> <I>tk_path_name</I></A> </TD>
+<TD> </TD>
 </TR>
 </TBODY>
 </TABLE>
@@ -367,7 +367,7 @@
 <TD> <A HREF=antennacheck.html> <B>antennacheck</B></A></TD>
 </TR>
 <TR>
-<TD> <A HREF=archive.html> <B>array</B></A></TD>
+<TD> <A HREF=archive.html> <B>archive</B></A></TD>
 <TD> <A HREF=array.html> <B>array</B></A></TD>
 <TD> <A HREF=box.html> <B>box</B></A></TD>
 </TR>
@@ -402,28 +402,28 @@
 <TD> <A HREF=deletecommandentry.html> <B>deletecommandentry</B></A></TD>
 </TR>
 <TR>
+<TD> <A HREF=display.html> <B>display</B></A></TD>
 <TD> <A HREF=down.html> <B>down</B></A></TD>
 <TD> <A HREF=drc.html> <B>drc</B></A></TD>
-<TD> <A HREF=dump.html> <B>dump</B></A></TD>
 </TR>
 <TR>
+<TD> <A HREF=drop.html> <B>drop</B></A></TD>
+<TD> <A HREF=dump.html> <B>dump</B></A></TD>
 <TD> <A HREF=edit.html> <B>edit</B></A></TD>
+</TR>
+<TR>
 <TD> <A HREF=element.html> <B>element</B></A></TD>
 <TD> <A HREF=erase.html> <B>erase</B></A></TD>
+<TD> <A HREF=expand.html> <B>expand</B></A></TD>
 </TR>
 <TR>
-<TD> <A HREF=expand.html> <B>expand</B></A></TD>
 <TD> <A HREF=ext.html> <B>ext</B></A></TD>
 <TD> <A HREF=ext2sim.html> <B>ext2sim</B></A></TD>
+<TD> <A HREF=ext2spice.html> <B>ext2spice</B></A></TD>
 </TR>
 <TR>
-<TD> <A HREF=ext2spice.html> <B>ext2spice</B></A></TD>
 <TD> <A HREF=extract.html> <B>extract</B></A></TD>
 <TD> <A HREF=extresist.html> <B>extresist</B></A></TD>
-</TR>
-<TR>
-<TD> <A HREF=ext2sim.html> <B>exttosim</B></A></TD>
-<TD> <A HREF=ext2spice.html> <B>exttospice</B></A></TD>
 <TD> <A HREF=feedback.html> <B>feedback</B></A></TD>
 </TR>
 <TR>
@@ -462,77 +462,82 @@
 <TD> <A HREF=load.html> <B>load</B></A></TD>
 </TR>
 <TR>
+<TD> <A HREF=locking.html> <B>locking</B></A></TD>
 <TD> <A HREF=maketoolbar.html> <B>maketoolbar</B></A></TD>
-<TD> <A HREF=move.html> <B>move</B></A></TD>
 <TD> <A HREF=measure.html> <B>measure</B></A></TD>
 </TR>
 <TR>
+<TD> <A HREF=move.html> <B>move</B></A></TD>
 <TD> <A HREF=openwrapper.html> <B>openwrapper</B></A></TD>
 <TD> <A HREF=paint.html> <B>paint</B></A></TD>
-<TD> <A HREF=path.html> <B>path</B></A></TD>
 </TR>
 <TR>
+<TD> <A HREF=path.html> <B>path</B></A></TD>
 <TD> <A HREF=peekbox.html> <B>peekbox</B></A></TD>
 <TD> <A HREF=plot.html> <B>plot</B></A></TD>
-<TD> <A HREF=plow.html> <B>plow</B></A></TD>
 </TR>
 <TR>
+<TD> <A HREF=plow.html> <B>plow</B></A></TD>
 <TD> <A HREF=polygon.html> <B>polygon</B></A></TD>
 <TD> <A HREF=popbox.html> <B>popbox</B></A></TD>
-<TD> <A HREF=popstack.html> <B>popstack</B></A></TD>
 </TR>
 <TR>
+<TD> <A HREF=popstack.html> <B>popstack</B></A></TD>
 <TD> <A HREF=port.html> <B>port</B></A></TD>
 <TD> <A HREF=promptload.html> <B>promptload</B></A></TD>
-<TD> <A HREF=promptsave.html> <B>promptsave</B></A></TD>
 </TR>
 <TR>
+<TD> <A HREF=promptsave.html> <B>promptsave</B></A></TD>
 <TD> <A HREF=property.html> <B>property</B></A></TD>
 <TD> <A HREF=pushbox.html> <B>pushbox</B></A></TD>
-<TD> <A HREF=pushstack.html> <B>pushstack</B></A></TD>
 </TR>
 <TR>
+<TD> <A HREF=pushstack.html> <B>pushstack</B></A></TD>
+<TD> <A HREF=readspice.html> <B>readspice</B></A></TD>
 <TD> <A HREF=render3d.html> <B>render3d</B></A></TD>
+</TR>
+<TR>
 <TD> <A HREF=resumeall.html> <B>resumeall</B></A></TD>
 <TD> <A HREF=rotate.html> <B>rotate</B></A></TD>
+<TD> <A HREF=route.html> <B>route</B></A></TD>
 </TR>
 <TR>
-<TD> <A HREF=route.html> <B>route</B></A></TD>
 <TD> <A HREF=save.html> <B>save</B></A></TD>
 <TD> <A HREF=scalegrid.html> <B>scalegrid</B></A></TD>
+<TD> <A HREF=search.html> <B>search</B></A></TD>
 </TR>
 <TR>
-<TD> <A HREF=search.html> <B>search</B></A></TD>
 <TD> <A HREF=see.html> <B>see</B></A></TD>
 <TD> <A HREF=select.html> <B>select</B></A></TD>
+<TD> <A HREF=setlabel.html> <B>setlabel</B> <I>(version 8.0)</I></A></TD>
 </TR>
 <TR>
-<TD> <A HREF=setlabel.html> <B>setlabel</B> <I>(version 8.0)</I></A></TD>
 <TD> <A HREF=shell.html> <B>shell</B></A></TD>
 <TD> <A HREF=sideways.html> <B>sideways</B></A></TD>
+<TD> <A HREF=snap.html> <B>snap</B></A></TD>
 </TR>
 <TR>
-<TD> <A HREF=snap.html> <B>snap</B></A></TD>
 <TD> <A HREF=spliterase.html> <B>spliterase</B></A></TD>
 <TD> <A HREF=splitpaint.html> <B>splitpaint</B></A></TD>
+<TD> <A HREF=startup.html> <B>startup</B></A></TD>
 </TR>
 <TR>
-<TD> <A HREF=startup.html> <B>startup</B></A></TD>
 <TD> <A HREF=straighten.html> <B>straighten</B></A></TD>
 <TD> <A HREF=stretch.html> <B>stretch</B></A></TD>
+<TD> <A HREF=suspendall.html> <B>suspendall</B></A></TD>
 </TR>
 <TR>
-<TD> <A HREF=suspendall.html> <B>suspendall</B></A></TD>
 <TD> <A HREF=tag.html> <B>tag</B></A></TD>
 <TD> <A HREF=tech.html> <B>tech</B></A></TD>
+<TD> <A HREF=techmanager.html> <B>techmanager</B></A></TD>
 </TR>
 <TR>
-<TD> <A HREF=techmanager.html> <B>techmanager</B></A></TD>
 <TD> <A HREF=tool.html> <B>tool</B> <I>(non-Tcl version)</I></A></TD>
 <TD> <A HREF=changetool.html> <B>tool</B> <I>(Tcl version)</I></A></TD>
+<TD> <A HREF=unexpand.html> <B>unexpand</B></A></TD>
 </TR>
 <TR>
-<TD> <A HREF=unexpand.html> <B>unexpand</B></A></TD>
+<TD> <A HREF=units.html> <B>units</B></A> </TD>
 <TD> <A HREF=unmeasure.html> <B>unmeasure</B></A></TD>
 <TD> <A HREF=upsidedown.html> <B>upsidedown</B></A></TD>
 </TR>
@@ -543,7 +548,7 @@
 </TR>
 <TR>
 <TD> <A HREF=xload.html> <B>xload</B></A></TD>
-<TD> </TD>
+<TD> <A HREF=xor.html> <B>xor</B></A></TD>
 <TD> </TD>
 </TR>
 </TBODY>
diff --git a/drc/DRCbasic.c b/drc/DRCbasic.c
index d23dbe81..8c97c866 100644
--- a/drc/DRCbasic.c
+++ b/drc/DRCbasic.c
@@ -768,7 +768,6 @@ drcTile (tile, dinfo, arg)
 	int edgeX = LEFT(tile);
 
 	firsttile = TRUE;
-	mrd = NULL;
         for (tpleft = BL(tile); BOTTOM(tpleft) < top; tpleft = RT(tpleft))
         {
 	    /* Get the tile types to the left and right of the edge */
@@ -858,6 +857,7 @@ drcTile (tile, dinfo, arg)
 		}
 
 		DRCstatRules++;
+		if (!triggered) mrd = NULL;
 
 		if (cptr->drcc_flags & DRC_AREA)
 		{
@@ -895,7 +895,7 @@ drcTile (tile, dinfo, arg)
 			    mrd = drcCanonicalMaxwidth(tile, GEO_EAST, arg, cptr,
 					&mrdcache[2]);
 			else
-			    mrd = mrdcache[1];
+			    mrd = (mrdcache[1]->entries == 0) ? NULL : mrdcache[1];
 			triggered = 0;
 		    }
 		    if (!trigpending || (DRCCurStyle->DRCFlags
@@ -1227,7 +1227,6 @@ drcTile (tile, dinfo, arg)
 
 	/* Go right across bottom of tile */
 	firsttile = TRUE;
-	mrd = NULL;
         for (tpbot = LB(tile); LEFT(tpbot) < right; tpbot = TR(tpbot))
         {
 	    /* Get the tile types to the top and bottom of the edge */
@@ -1318,6 +1317,7 @@ drcTile (tile, dinfo, arg)
 		}
 
 		DRCstatRules++;
+		if (!triggered) mrd = NULL;
 
 		/* top to bottom */
 
@@ -1350,7 +1350,7 @@ drcTile (tile, dinfo, arg)
 			    mrd = drcCanonicalMaxwidth(tile, GEO_NORTH, arg, cptr,
 					&mrdcache[2]);
 			else
-			    mrd = mrdcache[1];
+			    mrd = (mrdcache[1]->entries == 0) ? NULL : mrdcache[1];
 			triggered = 0;
 		    }
 		    if (!trigpending || (DRCCurStyle->DRCFlags