Activators don't pause their animation after opening inventory
Steps:
1.Go to Gedna Relvel's tomb in Old Mournhold.
2.Step on the stone opening the secret door (image attached)
3.Open inventory and watch the stones moving.
(RM-2874 from redmine: created on 2015-08-19 by Denis Smirnov, , closed on 2015-08-19 by nobody)