I just bought a new home for my sims and built them a pool, and noticed that when I had the girl go swim in it, after getting in the action would disappear and she would swim normally for a moment before automatically resetting and appearing next to the pool. I tried getting in the pool different ways to see if it was just the diving board she was jumping on, but the same issue occurred. I thought it was solely an issue with the pool until just a moment ago I had her sit and eat dinner with another sim, and after she finished eating the action disappeared but she remained sitting and talking to the sim for a bit, and then just like with the pool she reset and appeared next to the chair. It seems like the lack of action is causing her to reset, but I'm not sure what to do about that or if I can do anything. Mostly I'm just concerned if this is a sign of a serious issue like corruption, as I've completely avoided cheats to prevent such and have the ffs debugger to try and keep my game running smoothly. Any ideas/solutions for this particular oddity?

Possible that your Sim's trying some autonomous action that makes her glitch and jump-reset.

Got an error log? They're in C:\Users\[User]\Documents\EA Games\The Sims 2\Logs\, unless you've got the Ultimate Collection and even then the path's similar. One of them should tell you what's going on with the Sim.

Also, if you haven't, do the troubleshooting FAQ. Might be a hack.