I've got an endpin jack socket on my guitar, and although it's a pretty narrow slot where the strap goes I don't seem to have a problem with my cheapish strap with thin "leather" end. I had to open out the hole in the strap a bit with a leather punch but it's been fine.
My daughter's guitar has a seemingly very similar endpin, but she gets problems with it falling off all the time. The biggest difference I can see is that her strap has thicker ends than mine, but it still fits in the slot and has been snipped to fit the same as mine. My first idea for a solution was to cut some of the leather end off her strap (it's not an expensive one so not afraid to mod it) and sew on a bit of thinner, stiffer material more like mine. I see there are plastic straplocks intended for these type of endpin jack sockets, but they seem rather over-priced.
What do people normally do about straps on these type of endpins?
EDIT: I should mention that the strap stays on the guitar all the time (except when it falls off!), so it's not related to being repeatedly removed and refitted, and it seems just as tight a fit as the one on my guitar.
Comments
https://www.amazon.co.uk/MusicNomad-MN271-Acousti-Lok-Adapter-Metric/dp/B07PRPVP3B
or there's a cheaper "brass ring" versions (Fishman)
and one a bit like the plastic "fancy grolsh bottle" type
just because you do, doesn't mean you should.
Nil Satis Nisi Optimum
https://www.pinegroveleather.com/guitar-extras/guitar-strap-jack-endpin-adaptor
https://www.ebay.co.uk/itm/352004345817?hash=item51f5180fd9:g:IqEAAOSwTuJYxpUA
Ended up getting the Pinegrove leather strap attachment with the rubber washer.
The cutout is a bit larger than the endpin, but fits nicely when the rubber washer is fitted - seems to work well. Pack of 2 for a tenner including postage.
(Link as in comment above by @guitarjack66 above).
Some pics showing the item & fitting.