It suffered from simple CPU overload, in order to have priority inversion you need to have preemptive multitasking and synchronization primitives. The scheduler on AGC was essentially cooperative.
Side note: that is partly what the 90's term “Network Operating System” is about. Both Cisco and Novell managed to market the hell out of the fact that both IOS and Netware are not real multitasking OSes but essentially giant event driven state machines (nice related buzzword: “run-to-completion scheduler”), which they managed to market as being a good thing.
