Ragnarok Tactics

[LunaMoo]

Does it happen only at some specific place/specific skills?

If not, then I can't reproduce it, at least on desktop with windows seems to work perfectly fine, no idea how it works on other platforms.

Issue like that could be caused by some game breaking setting ~ to name a few: multithreading, changing emulated psp cpu clock, read to memory rendering modes, timer hack etc. or some broken CWCheats ~ even ones working on psp might fail on emulator due to mix of games running differently and cheats being badly made.
Eventually even by playing for a very long time using exclusively savestates ~ without reloading the game from normal in-game saves after restarting emulation as in general no game is bug free, console/handheld games are no exception.
Another possibility is file corruption ~ including install data if used(which is pointless waste of space to begin with), by some statistics from reports we had, broken iso's are actually very common problem ~ especially on mobiles.

So disable cheats, restore default settings(option for that in system menu), then restart emulation and reload game from normal save. If that wouldn't help, redumping iso/getting fresh eboot from PS Store would be the next thing to try.