I am using Libreoffice (ver 6.1.3.2) on Suse Leap 15. I can’t get it to work with files on my NAS. Calligra Suite works just fine with NAS files, as do all other programs I’ve tested. I see several other people have had the same problem with earlier versions of Libreoffice, particularly since ver 4.1. The problem also occurs with my daughter’s Raspberry Pi (latest version) in which Libreoffice freezes when opening or saving files to/from the NAS. So is there a workaround? Is it in the queue to be fixed?
If I understand correctly, this could be the issue raised with Samba shares and other network oddities.
The bug link is found in an earlier Q&A, and there are other threads which might provide work-arounds. It’s not easy… 
Fortunately, I no longer need to deal with this situation (no longer on that shared network!), but it’s a serious pain if you do, so hopefully that bug will soon be squashed.
I am not using Samba as this is a (mostly) Windows free house. Just using NFS.