Siemens Back-fed Main Breaker Hold Down Clip

Hay all. I was just wondering if anyone has had the experience of trying to replace main breaker of this type and the hold down snapping on you.

I have an old LC110FCGP breaker panel and the main breaker is starting to trip way under it’s rating. I tried to remove the hold down, but the handle snapped off. I’m thinking of using a drill to pry ou the remaining parts or maybe a thin screw driver.

Any suggestions. All are welcome.
Thanks in advance.

Jonathan