Try to either connect EBB to the octopus or flash the U2C with the klipper and define it as an MCU.
Right now, there is no data on how/where it loses communication.
That is it.
I assume that the EBB is in the middle between the U2C and the Cartographer, and both the Cartographer and the U2C have termination resistors installed.
If so, there is no issue with U2C to the CAN connection, but most probably with the CAN to the EBB connection, that is it.
Simply bad contact or some sort of EBB power issue.
You can take a look here, maybe it is releated: New Voron instance lost communication with EBB (can bus)