Question: Unusual behaviour of line and textplot commands in Maple 7

The plots at the end of the following code output the lines when the textplot is absent - but with the textplot the lines are omitted.  Am puzzled as to why this is happening.  Square_areas.mws  Square_areas.txt

Any help gratefully received.  David

restart:
 # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 # Areas of portions of a square 
 # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 with(plots):
 with(plottools):
 side:=6:A1:=16:A2:=20:A3:=32:
 # Pick a point in the square: say (x1, y1)
 poinC:=point([side/4,side/3]):
 cpoin:=op(1,%):
 x1:=cpoin[1];
 y1:=cpoin[2];
 lin[1]:=line([side/2,0],[x1,y1], color=black):
 lin[2]:=line([0,side/2],cpoin, color=black):
 lin[3]:=line([side/2,side],cpoin, color=black):
 lin[4]:=line([side,side/2],cpoin, color=black):
 #textA:=textplot([(cpoin[1]+side/2)/2,1,`A1`],align={ABOVE,RIGHT}):
 #textA:=textplot([(1.5+side/2)/2,1,`A1`]):
 tetA:=textplot([1,1.3,`A1`]):
 
 squ:= polygon([[0,0], [0,side], [side,side],[side,0]], color=white):
 # Plot without tetA - Lines are given
 plots[display]({seq(lin[i],i=1..4),squ,poinC}, scaling=constrained,axes=normal);
 # Plot with tetA - Lines are not given
 plots[display]({seq(lin[i],i=1..4),squ,tetA,poinC}, scaling=constrained,axes=normal);
 # Plot with tetA (placed  differently) - Lines are not given
 plots[display]({squ,poinC,tetA,lin[1],lin[2],lin[3],lin[4]}, scaling=constrained,axes=normal);