Can you reproduce the problem with this document?
And, when the crash happened, could you still ping the computer from another device in the network?
Crashing hard so that only a reset helps is usually only possible with a kernel bug or hardware issue, not something LibreOffice should be able to do.
Regards, Simon
I would agree. In my experience, so called "lockups" are usually the result of the video crashing. If you can ping then try ssh to the box and do init 3 then init 5 to reset the graphics and see if that clears it.
Mike