Synapse 3 performance issues in game.

So I was playing DOOM Eternal, it's been a while since I played it. Back then it ran smooth as butter, not so much anymore. I get big FPS drops, starting in the main menu by going from a solid 186fps down to 16fps after about ~30 seconds. And it looks about the same when playing, stable +100fps down to 20-30ish, then back up, down, up, down... You get the picture, it's very unstable. Running the game with Synapse 3 closed is the way to go, no problems with FPS in any way. Just stable, smooth, ass-kicking action ;) So, since I have to close Synapse I can no longer switch between my mouse sensitivity stages with the buttons on my Deathadder elite. It's an annoyance, albeit a small one. Any fix for this? Providing 2 pictures, one with Synapse running the other one without. FPS in top right corner.