My diamond cup wheel keeps spinning off when slowing down

I’ve run into a problem, I need to to remove some very stubborn thinset in my basement bathroom and also level some uneven concrete.

I decided to try out the angle grinder method, I have a Bosch 1375A 4.5" angle grinder, Ridgid 5" diamond cup wheel and a Herzo 4-5" universal dust shroud. My problem is the wheel spins off when the grinder is slowing down, I’m assuming it must have a brake, so the wheel doesn’t slow down as fast as the grinder and so it spins itself off. Has anyone encountered this problem?

Any suggestions on what I should do or suggestions on an angle grinder that would work properly with the wheel and shroud that I have?