title_body: Part of the screen on my reader is stuck
upvoted_answer: This looks like broken eInk display and I'm afraid that only display replacement can help here.
  eInk displays are rather fragile and not only dropping, but something that looks not so dangerous, like putting reader without inflexible cover with paper books in same bag, can mechanically damage display (even if glass is not broken). And display is rather expensive part of reader so if ereader with eInk display is not covered by warranty (good one) replacement may be not cost effective.