After dealing with the dreaded "disk not ejected properly" error for months while running Big Sur 11.6 I think i have finally seen the light at the end of the tunnel. I upgraded macOS to Monterey 12.0 this week and my Mac Pro (Late 2013) seems to have stabilized. While the "eject" continued to show up initially after I completed the install, the "eject" errors seem to have disappeared 100%. My setup was related to the use of a Promise Pegasus R6. I tried everything from cable swaps, to firmware updates, to Mac Power Management settings. Now I can only hope that future updates (and I know there will be many) to Monterey will not bring back the dreaded "eject" error.