Drive cleaning error 3 out of 4 weeks

[Michael Lynch_1]

I am having an issue with my 1/8 G2 autoloader where, during the week, my incrementals run fine, but on the last 3 out of 4 weekends, the full backup has errored saying that the drive needs to be cleaned. Of course, I've run a successful clean job, then all is well during the week, then it craps out during my full backup. DO I have a bad cleaning tape? How can I tell? Is there something more fundamentally wrong with the drive? How can I tell?

I am using used tapes. Thye have only had one backup job run on them. They are only 2 or 3 years old, kept in climate-controlled space. The drive is obviously older, but until now has performed flawlessly.

Thanks for any help!