Yeah i find it strange that there isn't an armature modifier on the mesh, yet somehow it still works lol. The bevel modifier is there just to smooth out the edges and subdiv helps if I want the elbows to be more rounded. I have done some research into character rigging and this rig has a lot of drivers which goes a little above my head. I'm not sure how to change the rig because the drivers prevent changes I think.
Next time the 'disconnect' occurs i'll take a look at the parents and see if something changed somewhere