I can never finish a push

Aside from the other comments, you said, "someone else on-site
pushes and adds new commits before mine can finish."  If I
interpreted that correctly, the "someone else" should also be
using a link as slow as yours.  Why isn't he having the same
problem you are having?

If you can track that person down (his name should show up in
the new commits you pulled), compare your config files to see
what is different.

Bill