I tried to upgrade my RB3011UiAS to version 7, but it refuses to do.
It's stays on calculating size and after a couple of minutes the web interface is available again with the old version.

I tried with both 7.1 releases.

both my CRS309 are now on 7.1.1
The RB3011UiAS refuses to leave its 3.49.2 version

It's a known "feature" caused by packages from extras. What I did: create backup, disable extra packages and reboot, upgrade, add extra packages, restore from backup.