I'm guessing the answer, but I think it's right.
For some months contribs.org has not been synchronised to ibiblio (& other ?) mirror sites.
I did raise this with people and again with Garret from Ruffdogs recently.
I see just now that there is some partial syncing at ibiblio, but not everything is there as yet.
So I assume there is a BIG file transfer of many Gb's (?) happening between contribs.org and ibiblio mirror(s), thus clogging contribs.org bandwidth.
Patience grasshopper.