Players who previously owned War Thunder on PS4 have access to both versions of the game on their PlayStation 5, and may accidentally launch older version in backwards compatibility mode instead of native one with higher FPS, graphical settings etc.
If you own the PS4 and PS5 versions of the same game, here's how to switch between them:
From the Games Home Screen, go to the Game Library.
Select the game and press X
Select the [...] button on the screen to view options.
Select the version of the game you want to download or play.
Here's a tip: If you are unsure of what version of the game you are viewing on this screen:
"PS4" appears beside the game's title at top of the screen.
PS5 versions only show the title in this area.