I used Microsoft Edge On Windows 11. I don't know why but character moved so fast that i died instantly. I hope you can find the problem. If it is not because of speed equation error it may be because of FixedUpdate \ Update difference.
I'll have to try it on Edge, the code is simple, your velocity vector gets multiplied by 1.03, the only thing that could have gone wrong is that it got applied more than one time. Thank you.
