I came here after suffering a similar issue. When I tab out of the game in fullscreen, the fps drops from a capped 120 (monitor refresh rate) to what seems like a capped 50 and a greyed out color palette ingame. Updated drivers, no change. Reset launcher and game settings, no change. Doesn’t seem to be happening in other games.
Switching from interval 1 to interval immediate and then back seems to fix it, as does playing in fixed window. Not certain if it’s Eve or a Windows issue, was fine yesterday, broken today.