Error rate warning LED code

[ClickHere2Surf.com]

I noticed the "TAPE" LED on my tape drive was flashing, I checked the manual and the flash patern I was seeing is "Error rate warning".

Is this a bad sign? I have had this a few months ago and ran the cleaning tape a few times and it was ok for a few months, should I be running the cleaning tape more often? The manual says:
"In case of SDX-420C/520C,a cleaning function which prevents and recovers from head contamination is built in the drive and hence, a periodic cleaning using cleaning cassette such as other format requires is not necessary. However, when the drive does not recover at the worst case, cleaning cassette is recommended to use."

I also noticed there is also a LED warning for "Cleaning request", so could this "Error rate warning" be unrelated to cleaning? But I would imagine cleaning request and error rate warning could both be caused by a dirty head.

Should I consider getting a new drive? I has been extremely reliable and I never had a real problem other than the LED signals.

I must say I bought this drive used (they cost a fortune new), should I consider buying a new one or another used one?

I do backup very important files which I can't afford to loose and I do backup to multiple tapes in case one fails, but these LED warnings and starting to make me wonder if this drive is on it's last legs.

What should I do?

Thanks

[ClickHere2Surf.com]

The LED signal stopped after running the cleaning tape, but I'd still like to know if this is a bad sign.