I had a similar problem with a Mega 2560 R3, Sainsmart 4.2", and the Elecfreaks v2.2 adapter. Having dug through the UTouch.cpp file, there is a section at about line 30:-
I then used an old library 'ITDB02 Touch Mod' and it now works fine. I found the library deep in the Sainsmart website. It would have been nice for Sainsmart to provide a downloadable library which worked!