Heading 1 heading disappears upon reopening

I have a LO Writer document which is losing the Heading 1 heading every time I reopen the document. Before I exit, I have confirmed that the Heading 1 heading is still there and it appears in the TOC and the document is saved. When I reopen the document, the Heading 1 heading is missing from the TOC AND the actual heading has been removed from the document.

The Heading 1 paragraph style is still there and I can redefine the Heading 1 heading and update the TOC index and it looks fine. But when I reopen the document, the Heading 1 is no longer in the document or in the TOC.

I am using LO 5.4.2.2

What is happening here?

Please upload a sample document on some server and edit your question with the URL.