Could be this is not a bug:

I had the same effect at the start of the "activity" - than i detected that on some sites not all categories or the "complete" site were "watched"..
At the activities menue ( left side) you have the "settings" at the bottom - have a look about your catgories or single paging watched.

I made the simple trick to stop all watching on categories ( not at the "translate" site) and single pages and to start site-wide watching … this worked easy over the bottom watching menu on any single page of the sites ( controleld over the settings than in teh activity board) and I get now all activities mailed and see it on the activtity board.

We had minor problems with activities last week and because of this some users might find random activities missing from the activity list.

According to our metrics, activities should be back to normal now. If not, and you are still missing new activities, let us know!

Seems fine, now, Michal. Thank you.