Touch NSTwGL strange refesh behaviour

[obelix]

I used NSTwGL (rooted) for a long time without any problems. Recently I broke the screen and purchased new NSTwGL. With this new nook I'm experiencing slightly different behavior of page refresh, it looks like double refresh of everything, including book pages, buttons etc. Very annoying. Its hard to identify if you had nothing to compare.

First I thought that probably the problem is related to firmware update of new nook. After many different tries as a final attempt I removed all partitions in the internal memory with noogie and installed someones old firmware image (1.1.5). The problem is still there!

1. Does anyone know anything about slightly different refresh behavior of new NSTwGL? Is this related to hardware?
2. Can anyone point me out to screen replacement procedure? (I'm thinking to replace screen of my old nook with the screen of new nook).