Thanks Donald…The upgrade to WordPress 5.6 – this makes sense to me as it started happening right after I made the change.
I left a some links to screenshots before – hope that post went through.
On my website – https://timeblockingsummit.info – the Register Now section / Feature Section is the part which was disappearing.
The truth is, I could not replicate the problem over the weekend. I can only hope this is a good sign…