Hi Domen,
your problem just happened to me yesterday, for the first time (or the first time I recognized it) in 11 months.
I opened a discussion on the same issue, since I had not seen your post, this is the link if you may want to take a look
https://www.ptcusercommunity.com/message/408061?et=watches.email.thread#408061
I have Creo 2.0.
bye