I have looked at your most recent log files and loaded them into PECPrep to examine the period distribution and in both log files the peak periodic error was not the fundamental 240 second period, but a value of 75.8 and 75.5 seconds. This is kind of a weird period. It is not an integer division of the fundamental worm period. The most interesting part, and is most likely just a coincidence, is that when you divide the fundamental 240 second period by the 75.5 second period you get a value close to pi, which is basically an angular motion equal to 1 radian. Really curious.
I am trying to wrap my head around what would cause such a PE.period in the G11. I am wondering if it is related to the coupler storing energy if there is a small amount of residual misalignment in the worm/motor coupling. Perhaps you can take a video of your worm and coupler with the cover removed and see if you can detect any small amount of movement 3 times during each worm rotation that could be causing this. To be sure, this is a very small amount of error and may not be worth the trouble to figure out, but I find it interesting.
Director Electrical Engineering
Explore Scientific, LLC.