Nephrostomy bag problem

Hi!  I’m visiting from the uterine cancer board. I have a nephrostomy and have a kind of odd problem with my leg bag.  Sometimes when I’m walking or even I bed somehow the bag comes open where the twist closure is. I don’t know if friction against my leg when walking or somehow when I turn over in bed it’s enough to twist it open but it’s very annoying. I’m always paranoid it’s going to somehow get open and leak. Otherwise the bag’s not causing me other problems (compared to stents which hurt like hell). I did have surgery to repair the ureter but it was unsuccessful so I’m probably stuck with this. Damage probably due to radiation therapy. Thanks in advance for any suggestions.