I recently started getting nozzle cover failures during prints. It's hard to pinpoint when it started happening. It possibly coincided with switching to the 0.6mm Ruby CC Core, and then the 0.8mm AA Core.
Attached is a photo of actually one of the less dramatic examples. In this case the print completed successfully.
In the other cases, a loose bed seems to have contributed to the problem. I have since tightened the 'clamps' on the bed and conducted manually