Ok after a ton of messing around it seems to trigger only when riding Merulina.
So the "safe" way to pop out the operator is to deactivate that first.
I hope this helps the devs since I main Titania who had her operator issues fixed.
I'm having issues replicating this but has happened to me several times.
Play as Yareli.
Activate her abilities.
Pop out the operator / drifter.
Now you can no longer access the warframe. Even on death or falling off the map.