After uninstalling Pretty Combat Animation (and of course running FNIS) my char can't move when loading a save. I've never had this issue when installing/uninstalling animation mods previously. And annoyingly enough the mod is hidden at Nexus ATM so I can't check it's forum or ask there. Does anyone have an idea what might cause it and how to fix it?

By uninstalling, do you mean you deleted all of the animation files that came with the mod or just unchecked an esp? Make sure you delete everything that came with the mod, including skeletons, before you re-run FNIS. FNIS should tell you if it's still seeing pieces of it when you run the update.

I uninstalled it with NMM, which always has worked fine for uninstalling/installing animation mods. But when I checked the folders, the male and female idle were still left, so I guess that messed up it somehow. After manually removing them as well - and rerunning FNIS - it works again.

I liked Pretty Combat Animation, with the exception of the combat idles, which look like they are forced on both males and females, sort of as if they suddenly are remote controlled or something. Anyway, fixed by removing everything.