So I’ve been rebooting between every carve now since I posted this and haven’t had the behavior since. Previously I would leave the controller running for weeks between reboots. In those periods of no reboots I would also be running multi-hour carves as well (5-10mb nc files).
I feel pretty confident in saying this is a bug/flaw in the RPI or the controller software (maybe a memory leak?) - given I’ve also had other issues solved by a reboot from the controller leaking file descriptors and temp readings being off.