I've found the version of lr-fuse (assuming that's the emulator you're running) to be especially unreliable with ROM types.
My recommendation is to try to get the game in z80 format, or Tap and see if it works best. TZX had a very high failure rate for me.
You may also change the model between 48k and 128k to see if it makes a difference for the specific games you're trying to play. I'd suggest saving that setting - if it's the one that matters - in a core game-specific save file.
Other than that, @mitu said it all.