So ì have a tlr 7 light and it's survived about 3000 rounds so far and still in perfect condition. I recommended it to my friend, and his tail cap has broke off 3 times, no idea why, no clue what's causing it, therefore I'm not sure how to fix it.
I also recommended a holosun red dot for him, blue locktite and torqued properly myself, and the screws still came loose. I did the exact same with my set up and I haven't had a single issue.

Anyone know how to fix these problems or what's causing them?
They're on a Sig p320 V-Tac. It's a full size handgun with the x series grip.

I just had the clamping screw loosen on my 509T after three range trips. I figured it would show signs of backing out quickly if it wasn't installed correctly, but it took about four hundred rounds and about a month.
Its a 509T on a C & H mounting plate on a Sig P226. Proper torque and blue loctite with a paint pen line on the screw head to show movement

I witness mark my 509T using white model paint and a toothpick

Easy to spot check if it starts to move and snug it back at the range

Not sure on the TLR-7 cap but make sure to clean the sight mounting screws with acetone before reapplying loc-tite.

The light issue could be an induced issue maybe from the holster.
The sight issue could be a few potential issues.  I would start by cleaning the hole, new screws, and do the install over again.

Holosun factory screws are not very good may as well buy better ones to start over with.  FCD is a good source.

@Duffy

Check and make certain the screws aren’t bottoming out in the holes. Using my Chambers plate my screws were too long by maybe .001-.002”. Just enough they felt tight and the sight wouldn’t wiggle. But enough under recoil they’d walk loose.  Make certain the screws (and holes) are squeaky clean. Torque tight. To spec or a bit more.  Locktite of course.

I used battleworx screws for my holosun SCS mos
Factory holosun bottomed out and ended up snapping