Whenever I play Final Fantasy IV (Anthology for PS1), it plays perfectly (as expected), however, occasionally when I move, horizontal lines come down the screen. I am using an SCPH-50001 with FreeMcBoot and the official Sony disc PS1 loader (aka pop in a legit ps1 game and play.)
This also happens with SNES Station, but all the time. I don't think it's related however.
Also, I do not get this problem in Twisted Metal 2.