On macOS, noticed since version 5.2.x (may be even on 5.1 series) Writer, having an open document, freezes for a certain longer period (OS is responsive, except for LibreOffice) which might last even for a minute, then resumes as if nothing happened.
I use to have several documents open, but I do not know if that is in any way connected with the problem.
I cannot reproduce this constantly but it happens on two systems I have access to (with 10.12, but even on previous OS versions', like 10.11), an Air and MacBook.
Maybe better description would be: becomes unresponsive?
Yes, this is a known bug when several documents are open simultaneously in LibreOffice and/or in hidden window state.
*** This bug has been marked as a duplicate of bug 103571 ***