Email addresses disappearing within active iCloud accounts

This is now the third time during the last several months, possibly a year, that this has happened. I have 2 iCloud accounts (one primarily business, the other, primarily friends), each with some custom aliases and also Hide My Email aliases. What happens is that new emails drafts will only show the addresses in the "From" field from one of the accounts, not the other. When I go to Mail preferences>Accounts, the Email Address field for that account is blank. Opening that field shows that the Email address list is empty, and I have to add them all back in manually.

I don't use a VPN, but I do have Private Relay chosen. I've seen this brought up in the Support forums by at least a dozen people. But no one has had an effective fix. There seems to be no pattern to how this happens, or what the interim period is of it working after re-doing the list before it happens again. I can't be positive, but I think it has happened to both accounts at some point.