it happens!! more common with the pressed loop type battery clamps, as the battery terminal can bend, so the nut pinches the clamp legs, but the terminal ring is still loose enough to vibrate off... you'll probably need to bend the legs a bit to get a better clamp... it'll make sense when you look at it !
aka Jonathan!!
'92 charlotte green auto.... as a daily
'37 Ford Y street rod......... something for the weekend!
...... if a photobucket pic is foggy, click it, and it'll take you to the clear version, yes, it's a clicking faff....