We've had similar issues with nodes cutting out after this error message (Frame synchronisation failed) too. Literally just had 3 of 4 nodes drop out just now, always 1 by 1.
It always seems to occur on still renders only, animations are fine. It also only seems to occur when the TR config is set to 'Automatic'.
I've previously set the config to 'Manual', with update interval at 20s and packet size of 5mb. This prevented cut outs of render nodes, but the render would be no quicker than if I rendered on a single machine.
Reading through some comments and some responses from TomG, it's suggested having a larger packet size for larger resolution renders. So, personally, Im gonna try 100mb at 40-60s intervals and se how I get on. I'm not entirely hopeful, but Ill report back if I find it beneficial.
Rick