yep, this was happening in Beta 4 too. I hoped they had it fixed for the GM but nope.
It happens all the time when you have multiple tabs open. Tap a link or do a search ( seems more often when searching?) progress bar stops moving.
Stopping/refreshing fails to work as well. Open the same link in a new tab and it loads fast as anything. you have to close the problematic tab as it never seems to come back to life.