Uwah. I'm sorry you ran into something like that... This is sadly a bug that I thought I had fixed. It happens if the battle before the one you're in now ended unexpectedly in the middle of an action. Do you recall what was the last battle that you fought before this one? Loading any save before that battle should fix it, but I would still need to know which encounter it was so I can look into patching the error out.
Knowing your current party composition and if there's any character in your party now who hasn't been in your party before this battle would also help!
uhmm honestly sometimes i just spam my space bar but right now in my party i have gaia, celeste, belle, and malayna. it was fine until after the party composition thing after i saved malayna from the 3 vessels of sin. i also changed the party composition where it would be celeste, malayna, gaia, then bella.
I assume Bella is the name you gave the priestess? Considering you mentioned Malayna though I can't help but wonder, did you install the latest version of the game? You can just extract it over the old one, if your version is over 4 months old it may still have the bug I fixed~ That said though it does not retroactively fix saves that already display the bug I fear.
I'm sorry for the inconvenience, if I could do more I would but sadly I'm no longer in contact with the one person who could help me fix issues like these properly.