Cross-References Crashing Indesign (18.3 x64)

I found that while creating a cross-reference, when I created and saved a format in the Cross-reference popup, Indesign would crash. I would then re-start Indesign, re-open the document, go "type>Hyperlinks and Cross-references>insert cross-reference" and I would get a blank panel, with Indesign crashing. I can no longer use the cross-reference function without crashing indesign in this document.

Before this I had also noticed that there were no default formats available. So, I closed the document, started a new document, I could insert a cross-reference, and there are default formats available in the cross-reference panel.

I then noticed there was an indesign update, but the same problem persists. I exporeted the doc as an IDML, and re-opened, same issue.

So, have resolved to doing manual cross-references for this document, but of a pain, but luckily not too many.

Windows 10, 64GB Ram