Thru Axle Constantly Coming Loose

The QR on the thru axle on my rear wheel is constantly coming loose and I’m not sure why. It is plenty tight to start with and closed parallel to the chain stay (and forward) so it’s not like something smacks it and loosens it up. This happens frequently enough (every second ride or so) that I have been watching very carefully to see if anything hits the skewer to spring it open but I can’t say that it is happening

Does anyone have any ideas as to why this is happening or how to solve this problem?