When I enable Dualshock while using PSX Beetle HW I get slowdown!

So I enabled Dualshock to try and get rumble while using Beetle PSX HW. And when I start to play a game I get massive slowdown. When I turn duelshock off the game runs smooth and goes back to normal. Does anyone know the reason why this is happening? So, I can never use rumble?!!!

Can anyone test this?