Endlinks keep coming loose.

I run with coilovers and rather stiff settings. My aftermarket (non adjustable) endlinks keep coming lose - the lower bolt shimmies loose. Is it because I'm running at a ride height not ideal for the set length of the endlinks? My thinking is that the endlinks are under inappropriate pressure and that I need to get adjustable endlinks so to relieve the undue pressure on them. Will this solve my problem? I've tried torquing the lower bolt and I'm a step away from trying thread-lock. Any tips?

edit: i know they're loose because I eventually hear a clunk when turning. I've tightened them and no noise.. for a while.. then clunk again due to them being loosened.