Bug Copy and Paste in Blocks

Whenever I try copy and paste elements inside the Block Editor (in different blocks or in the same one with no differences) by pressing CTRL+C and CTRL+V, the Block Editor window disappears, and to be able to continue to work the only solution is to use the command “unlock selected objects”.
Is this a known bug?

It does sound like this one: RH-45620
It is fixed in Release Candidate 2 of SR5 - which version are you running at the moment?

I´m running
Version 6
(6.4.18130.19341, 10-05-2018)

If you want to, you can subscribe to Release Candidates (Rhino Options > Updates and Statistics) and check if this fixes the issue for you.

Thank you for your help! I will try to do it immediately.