This situation has been solved. I found out that hogue grips are not suitable for these m9 berettas as the slide stop does not sit tightly onto the body (hogue grips are not sturdy enough to place pressure on the slide stop). This would lead to the slide stop popping out.
*Just a heads up for anyone who will try to do this*
And sorry for posting again. But there is no edit for the first few posts I made... weird.
Thanks Brad for your help/explanations!