First off, sorry for the much delayed reply, I didn't realize some new posts were getting flagged by our spam filter.
If this is still giving you problems you might have some luck putting some 'lock tight' on the screw threads. I would recommend a blue lock tight (it stiffens the threads so they don't come loose, but doesn't permanently lock or bind them in). We often use Lock Tight 248 (blue) for this.
Hopefully this fixes the issue for ya, but please let us know how it goes (I won't take months to reply, lol).