I have a 2.6" color 320x240 serial display whichI am extensively testing all the commands. Ive found that the rectangles are obvoiusly drawn incorrectly about 2 out of three times. The endpoints of the lines do not overlap properly. The lines drawn on the major axis are 2 pixels longer than those drawn across the minor axis. I can't tel which of the 2 sets of parallel lines are being drawn wrong.

Has anyone else seen this ?

 There are few drawing window bugs before firmware version of V3.2, but already fixed after V3.3

The display is running V3.4A.

I'd send a photo, but I don't know a way to attach a file.

According to the picture you sent, the problem is that you set the height value of box to negative. The valid value must >0.