I think I heard that the vehicles vanishing when you load back up is determined by if you or another player ever actually sat in a vehicle to basically leave an "I was here" footprint to determine you used it? Or something like that?
But whenever we load up missions I'd say 98% of the time it starts us back at the FOB and not our last known position prior to saving. I think in probably 50-60 ALiVE Missions run...it's saved my location twice.
Every stat is being saved, markers are being saved, etc. No other issues.
Is this a known issue?