This a weird one. Should be reproducible with any sufficiently long scroll view. But for me it only happens on battery, with low power mode (macOS 12.6, MacBook Pro 14").

During repeating swipes, at some point macOS will stop sending - (void)scrollWheel:(NSEvent*)event event when two fingers are down on trackpad, but it will keep sending appropriate -(void)touchesMovedWithEvent:(NSEvent*)event message (with two touches as expected).

I have no idea why this only happens in low power mode. I also don't know if this can be reproduced on older macs.

I tried disabling resting touches but it made no difference.