2003 rtv900 trans issue

I own a 2003 rtv900 with 240hrs that I inherited problem is when you put it in any gear and push the throttle down it doesn’t move you have to more less feather the throttle for a few seconds for it to move I have changes trans fluid and used factory fluid and filters it acts like it’s low in fluid before pump picks up but it is full any help please

2003 rtv900 trans issue