100-400L Zoom Range Issue

Received my used 100-400L today. I initially went to zoom it in and out but it wouldn't go all the way to 400mm, stopped at 350.
Then after a while it fixed itself, don't know how, but then it wouldn't retract to 100mm, only 135 or so. Now it goes to 105mm from what the EXIF says.
The tension ring is all the way to smooth. Any ideas?

I had exactly the same problem with mine. Since it was out of warranty, I took to a local camera repair shop that is an authorized Canon repair center and they told me it was loose guides. They repaired it and it's fine now.

If you just purchased this lens, then return it asap. Otherwise, it's going to have to be repaired.

Thanks for the info. What is "loose guides"?