Zotero hangs when there are special characters in the title. I am using Zotero on Firefox and LibreOffice 5.3 on Ubuntu 16.04. Sometimes even roman numerals (XV) also causes it to hang.
What special characters do you mean? How many references are in your document? Does this happen even in a new empty document? Can you submit a Debug ID for an action that causes LO to hang?
This is a known issue, fixed in Zotero 5.0 to be released soon. You can get the 5.0 Beta, or just download the patched LibreOffice Zotero Plugin and install it into LibreOffice directly.
Upgrade Storage
https://www.zotero.org/support/debug_output