info_survivor_position are part of maps and not something spawned by game code though. I wonder if it's not guaranteed because the event/trigger is too late in some cases. Maybe hooking escape vehicle arriving and spawning then, and final spawn if any extra players joined/spawned since then when leaving.
Surely theres some function which could be patched to prevent having to even spawn anything extra, some code must have changed to break this since pre last stand or is the issue with 4+/8+ extensions not fixing the issue since update? I don't run any servers to know even though I have 4+/8+ stuff enabled, but its only ever me testing and getting together enough to test is never possible, one of the reasons I've never bothered with 4+/8+ stuff even though I would have wanted to.