Requesting advice for Err01 on Canon 70-210mm f3.5-4.5 USM

Hi all,

Here's one for you.
I recently purchased a 70-210mm from eBay after reading plenty of good things about the bang-for-your-buck ratio of this lens.

After some testing, I've found some interesting things:

• Between 200-210mm, taking a photo - at any aperture - on both my SL1 and a friend's t1i produces an immediate Err01 message ('clean the lens contacts').
• The problem occurs on both manual and autofocus.
• The problem does not occur at any shorter focal lengths, tested across the gamut of aperture settings.
• On a friend's t3i, the problem does not occur at all.

Cleaning the contacts - with a soft cloth, both with and without a bit of rubbing alcohol - has not resolved the problem.
I've used a fair number of other lenses on my SL1 and haven't had a problem (Sigma 17-50, Tamron 11-16, Canon 18-55mm, 18-200mm, 50mm, 85mm, 24mm STM), so I can't imagine it's my camera's contacts (although I've cleaned those too).

The lens is no longer covered by Canon for parts and service, and I can't seem to find the part numbers for its components, even supposing that I felt confident enough ordering them and attempting a DIY fix.

The first threads that I've found about the error (only on other lenses) typically point to pinched aperture cables - but if that's the case, then I don't see why the problem is completely independent of aperture, and isn't reproducible on the t3i.

My options as I see them currently are
a) stick with a lens that I can use between 70 and 200mm, and hope that the problem doesn't worsen; or
b) return it and take the 40$ hit for return shipping.

Any thoughts/suggestions/brilliant fix ideas are appreciated!