I ran across this issue today. I have a Beta SPS UVW-1800. What worked for me was clearing the log.

Enter Maintenance Menu (Left Arrow+Menu)
Support scroll down till you reach DIAG CNT, hit right and you'll see Clear LOG.

This should eject the tape safely. Hope this helps.

connect your video monitor to output #3, make sure on-screen characters ore enabled. access the maintenance menu by holding the menu button and left arrow button. when maintenance menu comes up, use the arrow keys to scroll down to "moto check". select "threading motor", unthread, then select "cassette housing motor" and eject your tape. be sure not to break the tape when ejecting.