I have this problem since the beginning of the sim. As yet I have not found a solution and have given up for the time being. None of the patches have changed this.
For me, as I approach aircraft they first appear at a distance, then as I get closer they dissappear and then as I get closer still they will re-appear.
In the first video the E/A is approached from astern.
Make sure to enlarge the screen and set the vid to HD
In the second video the E/A in a headon pass flickers and then briefly disappears at 2K....It is easier to see with the icons 'on'....As there is a fast closing speed the invisibilty zone is passed through quickly but as you will appreciate going through this zone from behind an aircraft will render it invisible to me for for long periods of time.
The solutions I have tried are: Different monitors, MeshShowLod=1, Post processing AA and lower resolution.
None of the above worked.....