Hi! Thanks for the quick reply! I have version 1 of the NyBoard. So I still wasn't able to calibrate the MPU - even after letting it run for 12 hours... there was never a moment of stability. So impatiently I uploaded Nybble.ino to the cat and it worked this time. Of course it is falling over a bit but it can walk around etc. I am hesitant to try and reproduce the error right now because I have a cat that can sort of cat now. I will try to collect some more data in a day or two after I get to actually use the platform a bit now, but further symptoms are that I was unable to reliably communicate when it was calibrating. Sometimes the calibration script would load and I could hit n then n then the cat would spin up the servos and pull all joints in, then the serial monitor would ask if I want to calibrate the MPU - sometimes once, sometimes 2 or 3 times. I could not always get it to respond - typing n or Y would result in nothing. I have the serial monitor set at 56700baud and No Line Ending. I saw other posts about servos drawing too much power (?) and stopping scripts/comms. Let me know if there is any other info that would help right now - otherwise I'll post more info after I upload WriteInstinct again