I am thinking this is all related to the fact that GC does not correctly sync parameter values with the Firmware. I am confident you never set the SystemSettings ChainLength to 64602. I am guessing this is the random number that was in that memory location when the Arduino was programmed. Because GC doesn’t respond correctly when it recognizes this difference, it is giving you a hard time.
I am guessing there is another parameter that is in the weeds, that is causing it to calculate a chain-length of 72953.81 mm.
BTW, to my knowledge, there is nothing I have done which impacts this. I believe this problem is present in the main fork of Ground Control. I don’t understand why this seems to be cropping up at this time. Have you, or others, had problems like this before?