Many users seem to be failing incremental updates to 4.5.1

More than half of our users appear to be failing the incremental updates. From one of our mirror's webserver logs for yesterday:

$ grep "incremental.mar" dist.torproject.org-access.log-20150514 | grep -v "GET /torbrowser/4.0.8/" | grep 4.5.1 -c
81575
$ grep ".mar " dist.torproject.org-access.log-20150514 | grep -v "GET /torbrowser/4.0.8/" | grep -v incremental | grep -c 4.5.1
50235

Could this be due to the HTTPS-Everywhere update in 5.0.4? I wonder if something about how it is being unpacked is causing the force-update in the incrementals to fail..

(The grep -v for the 4.0.8 update is due to another issue.. We have a lot of users also trying to download 4.0.8 mars for some reason).