400 2.8 is - focus ring loose

Just picked up a used example.

The focus ring appears to be loose (shifts a mm or two up and down if you were to have the lens sitting upright)

The lens works fine (or seems so) just wondering if anyone else has come across this? Main thing I'm a bit worried about is if this will effect weather sealing as in the uk it's pissing down most of the time

I loaned one from CPS couple of months ago. It was a pretty beaten up lens, I didnt notice the focus ring but the lens it self was pretty loose on the body. I tried with 1D MKIV and 7D both did not fit very snug. there was a minimal movement.

The mount is worn but that doesn't bother me.

It's the small movement in the focus ring that I'm wondering about. As I'll rarely be shooting mf it's not a big issue as long as the weather sealing isn't effected.