I don’t know if maybe you’ve already come up with another way to fix escort quests in-game. But a possible solution is that you put a hard cap on event duration (well above event time constraints) and if the event doesn’t progress in that time limit, it either fails or resets to starting parameters.
You can make the time a large amount, like a half an hour or even maybe a full 60 minutes. Either way, this hard cap would allow for bugged/stuck escort events (nearly all the events I see that are bugged) to reset / fail themselves as not to halt progression of other chains/events in a given zone!
TL;DR Make escort events reset/fail after a certain amount of time has elapsed.