Thanks Michael for your fast response. Before deciding to post my request for help, I had done my homework (however with my limited understanding). I had already followed the entire process described at Data Lost: How to restore missing Directories . This allowed me to seemingly repair all files within my Vault, and the Health Check showed “everything green” after that - I should have clarified that point.
Despite this, the files now shown in the recovered LOST+FOUND directories seem corrupt.
I have most likely cumulated too many mistakes… I guess I’d better start from a clean backup and rebuild a new Vault from scratch on my local drive before uploading it to OneDrive.