Calc 7.6.4.1 now all calc documents request file recovery & all fail recovery

All my documents are relatively small in size (max 500k) & all have been used for at least 10 years. Upgrading to latest ver when available. This happens on my desktop & laptop, both win10 with all available updates to date. Libre office ver 7.6.4.1
All documents are, even though recovery failed, available & process normally.
Thanks

Please provide a sample of such document. It might be a bug.