Thanks for the quick reply.
I have been dismantling the Roomba, (for cleaning), for a while now and have a basic knowledge of the 560. I have put the side brush on correctly "snap" and I cant think of anything different in my actions or in the environment that may be causing the problem.
I do understand the reason for the screw, but am still a bit confused as to why it is seeming to self tighten? Could it be because of the collisions? (meaning I should watch for trouble areas and make changes to help the 560? Note that I have made every effort to Roomba-proof the space, but maybe I need to go that step further)
I will try a thorough clean then loosely fit the side brush screw, reset and keep a watchful eye on its progress.
I never thought about a system reset. Hopefully this will help sort it, as I'm going to be very confused if the problem isn't fixed after the above steps.
Thanks for the advice.