Steam prevents SDL from working in my game (windows)

I have a game where I use SDL2 only for the gamepads. Everything works as it should. If I start the game via Steam (with the testapp ID) SDL2 does not work anymore. Now I have seen that Steam also has a SDL2.dll. Can it be that my SDL implantation is somehow overwritten? Can I prevent this?

Windows 10

I’m not sure if it could be overriding your included sdl2 dll, but one easy way to find out is to put together a build of your game that logs your SDL version and check the log. If the version is different when you run it from within Steam, then it must be overriding your dll.

See SDL_GetVersion - SDL Wiki' for details.

I have noticed a few more strange things. When I use the Steam SDK then SDL2 no longer works. But when I start my game via Steam then SDL2 works again. It is possible to start any .exe via Steam. I don’t understand it.
Another thing is the Steam SDL version. In the Steam directory is a SDL2.dll and the version is given as 2.0.15. How can this be possible? There is only a 2.0.14 version.

The latest version in the repository is 2.0.15 SDL/SDL_version.h at main · libsdl-org/SDL · GitHub