OLED displays can be easily damaged through rough handling and even during shipping. The lower corners of the glass are unsupported and can crack easily. If this happens, it will render the display either inoperative or will cause every other line drawn to be missing.

A quick easy way to minimize this issue is to add a very small dab of glue under each lower corner of the OLED. The use of Ultraviolet Glue is a quick and strong medium. Click the picture and you'll see an example of one that has a cracked corner, and the other with the glue applied. Doing this will save a lot of trouble when building. - Mark