Started to happen to my MKII Gray as well. Found Octatrack MK2 blackout & yellow leds which described the same issue, where the author ended up sending it to Elektron. I wrote to support describing the same thing + linking that thread, they confirmed the issue and now I’m waiting for DHL to come and pick it up. Seems the CPU might be wonky for you as well.
Only had my Octatrack connected via USB once (for transferring the firmware for an upgrade) otherwise it has remained unconnected since I first got it.