i have a pair and they keep working loose. anyone else had this happen?
they are the older model.

Mine are fine, actually tricky to get off.
Have a look at the interface between the crank and the spindle and see if there is any damage.

there was a burr but it has been lathed off. no change though 🙁

Never had a problem with mine.

Guess you’ve tried blue loctite to keep bolts up nice and tight, sometimes if they’ve loosened off a few times it creates a bit of play and makes them more prone to loosening off.