Yeah could be an issue with FAF. In vanilla I can overcharge. On a different note, with M27, something that is a bit annoying is when I build an T3 arty, AI will send over engineers to help me build it sometimes, and thats ok, but the problem is when they also start building their own T3 Pgens next to it. Im not sure if that matters whether or not an allied PGEN will give the connection boost to the arty or not, but I dont think its intended.
Another little issue Im seeing on occasion, the AI will send out a cluster of T3 engineers toward the enemy bases that behave as though they are combat units on the offensive, and they just die.
https://i.imgur.com/qBuXOVK.jpg