I put a Nordic components bolt handle on my SLP and I haven't had any issues with it falling off. I can remove but only when cleaning my SLP. Definitely nicer than the stock handle that the SLP comes with by default.
The Nordic bolt handle is a good addition to an SLP. Makes it easier to cycle the action while the gun is on your shoulder.
Like yours, mine had the annoying habit of popping off after 15 or 20 shots. One thread I read about this problem advised to paint the handle bright orange so you could find it in the grass a little easier. That would help, but I like the way my SLP looks in solid black.
I just used a file to the deepen the notch (detent) on the handle stem a little, and made sure it was slightly rough. Now it says in place just fine, and yet I can still yank it out when it is time to remove the bolt.