It's not just about the fit of the bayonet. The locking collar doesn't really lock. It just slides over and will just as easily slide the other way if there is friction or if the material from a lightbox grabs or rubs against the collar.
I could make it happen with an Elinchrom modifier too. If I rotate the modifier clockwise it won't happen but if I rotate the modifier counter-clockwise then there's a very good chance that it's going to spin the collar in the reverse (unlocking) direction and if you're not careful it will then rotate the entire bayonet the additional amount to release it from the strobe's mount.
In normal use I don't have to force it to happen. It just does, and it happens with any or all of my RX's. The funniest part is that the D-Lite it incorporates a different method of locking by using a 'switch' of sorts, and it's rock solid with no chance of being pushed in the wrong direction and unlocking.