After replacing Display touch ist working, but display issues

After I replaced the display of my iPod (4th Generation) touch the display ist grey on the left half. At the end of the grey area are some grey, vertical lines. The lines change there position when i change pressure on the display. However touch is working on the entire area of the display. I guess it is a problem with one of the connectors. Is it possible to tell which of the connectors caused this issue? Because I had some issues to proper connect the inner connector (the one connecting bottom-up to the logic board) cause the connector allways fell off while I tried to wrap the copper around it so i fixed the copper with some tape. I hope to avoid as much of the removing and reassembling process as possible because i really don't want to damage anything. So if anybody can give me a hint what the reasson may be or how to find the reasson with a minimal risk of damage i'd be thankfull!