Seagate BUP Slim BK SCSI External HDD I/O errors only when plugged in during boot

Experiencing strange behavior with my external HDD. When I boot the system the external drive and directory structure shows in file explorer but when I access files or directories I get an I/O error message. If I unplug and replug the external drive, it works fine. If I boot the computer without the external drive connected then connect the external drive, it works fine - no I/O errors....

Any ideas why this is happening seemingly exclusively when its connected during boot?

See what happens with a clean boot. If it doesn't happen in a clean boot, you have some software conflicting with Windows during startup.. Brink's procedure will help you weed out which one. Perform a Clean Boot in Windows 11 to Troubleshoot Software Conflicts Tutorial