Happened about a week ago when opening a file on a non-OS disk, running Monterey 12.7.1 (MLOC) on cMP 5,1, PCIe NVMe SSD. I immediately noticed there was no startup chime anymore and I was unable to boot into safe-mode. Safe-mode login screen would flash for a second during boot but then loaded OC boot screen. I'm assuming Opencore is the reason I can't boot into safe-mode? First-Aid returned 0 errors so I reset NVRAM and chime came back with no problems thus far. I have an app called Rember in my utilities folder that I plan to run in safe-mode to make sure memory sticks are not failing.