That was arguably an application specific issue, though the OS was painful to code for. I actually coded some classic Mac OS networking code and it was insanely easy to mess things up, but eventually it ended up being rock solid. The trick was all level interrupts where supposed to only do almost nothing. You couldn’t allocate memory for example which was a major hint of just how minimal those functions needed to be.
Worse with cooperative multitasking any running application could mess things up.
Worse with cooperative multitasking any running application could mess things up.