Yeah I'm a tad over 900 hours with IL2 GB, a good amount in 109s. I've only witnessed this once on the WWII side and that was when my wingman was visible to the flight , but he couldn't see anyone else.
I have had this bug occur to me or my wingman 4 times now in FC since I started really flying in November.
The issue clearly more pronounced here. Speeds are slower, combat is slower and SA is better so watching a plane suddenly appear on your six while your looking at nothing behind you sucks.
Last nights engagement