What's happening is that the game regularly spikes to over 100% CPU usage on my machine (I know... but it's looking at "top" on a quad core, hyperthreaded i7-965EE 3.2gHz machine with 12GB RAM and a 3GB Radeon 7970 GPU)... it'll sit at around 116% for several seconds, during which the game runs very slow/laggy... and if you don't touch anything for like 10 seconds it will go back down to around idle and things will be OK again sometimes for a few screens, sometimes as soon as you load more dialog.
Maybe if I had a more powerful CPU (this one, despite still being powerful, is actually around 10 years old. It was the top end when I bought it) the load wouldn't go high enough to cause it to freeze like that for several seconds and you wouldn't notice the load?
Does it really not show ANY load like that for you? Or just not enough for you to notice?
I've played it without the patch and there was nothing at all. Just smooth sailing. Let me try it again now... Well, I played up through the school and talking to Smith and June etc... and didn't see any load issue on either, but it was definitely there earlier when I played my saved game.
Maybe I'll start another fresh game (I was playing my 0.15.1 saves on 0.15.3) and see what happens. But not tonight.
Have to be up early tomorrow.
I saw the load spike once to around 75% on both copies (just after entering the school)... otherwise it stayed mostly around 13 to 22% with a few spikes up to around 38 or 40.
EDIT: Also tried the image cache size trick, and the framerate (had already tried that before) and neither change the problem on my saved games. Immediately ran into the problem again. I'll try a fresh start from 0.15.3 when I have time and see what happens.