We've had 3 users this week report that when marking a large number of emails as read, the SM web interface stalls/freezes (Chrome even pops up with an alert asking if it should terminate or wait), it does eventually recover. I was able to reproduce it once by doing a select all on a folder with a large amount of unread+read email and clicking mark as read. The progress alert pops up and completes, then the interface stalls, the unread folder count doesnt update, you cannot navigate to any other areas etc.

This appears to be a new issue to this build.