Beetle PSX performance issues

I’m having a very strange problem with the Beetle PSX cores in recent versions of RetroArch, including 1.7.7. Ever since version 1.7.4, games will seemingly run just fine until I perform certain actions within the game. For example, in Ape Escape, when I use the Sky Flyer, it causes extreme slowdown that persists until I close and restart the core. There are times when an action in the game will crash RetroArch, such as when I shoot the net underwater. I don’t think this is a problem with the cores themselves, because when I use version 1.7.3, I have absolutely zero issues. I’ve tried everything I could think of to fix this issue: different renderers, settings, core options, nothing works. I really don’t want to keep an old version around just to be able to play PS1 games. Can you please help me figure out what’s going on here? Thank you.

My specs: Intel Core i7-7700K 4.5 GHz, Nvidia GeForce GTX 1080 Ti with latest drivers, 16 GB Corsair Vengeance DDR4 3200 MHz, Windows 10 1809

Check this. Maybe a related problem?