Spurious reminder email (since latest CB upgrade)

Both plans show their 'parent plan' as "top".

Is that OK, or should I make one the parent of the other?

I don't think it's all that uncommon for a user to expire a paid subscription, and log in but choose to resume as free for a day or two (maybe they didnt have their credit card handy!) , before upgrading again to Paid user later...

currently we have 4 Mailer auto-notices programmed:

Your Subscription is about to expire in 30 Days
Your Subscription is about to expire in 10 Days
Your Subscription is expiring today
Your Subscription Expired 10 days ago

It's fine for both plans to be top level. Were you able to confirm that's what they did? Logged in upgraded to free then later upgraded to paid? If both are exclusive it should've upgraded the paid plan to the free plan then back to paid plan after they paid. Notice the first subscription (14956) status still shows as Active, but it's past the expiration date so I'm not sure what to make of what happened.

Sorry, I wasn't able to confirm exactly what that user did. I think his original complaint was back in early December. We have ~20,000 users, and I get buried by about 100 emails a month from them (mostly they are frustrated trying to renew or upgrade subscriptions, or recover lost passwords, or change their email address). But my primary job here is Oracle programming our company ERP, and my secondary job is producing media, so unfortunately the web site (barely making tertiary status!) doesn't get my undivided attention...

I seem to vaguely remember that at some time years ago the default 'fallback' was that when a Paid subscription expires, it automatically converts to Free.But I don't see a setting for that anywhere obvious. Maybe it's some artifact from earlier version of CB? We also have some old accounts that don't have either subscription, only 'registered'. Not sure how they got that way - unless that's just the state of limbo where their Paid account is expired?

PS: maybe the solution is for the software to 'unmark as expired' the Paid account 'expiry' whenever the same user downgrades to a Free account?

CBSubs does not fallback to a free plan on expiration. At least not one that you can configure. There's a hidden free state that they'll fallback to. Expiration's need to be triggered. It's possible the expiration was never even triggered. Typically you want to be triggering expiration's once a day using CRON (see CBSubs > Settings > Global). For your mailers that trigger after expiration I recommend setting "Must be in state" to "Expired" as if it's currently set to "--- Not relevant ---" then it's strictly conditioning off the value of expiry_date as the condition implies and that could be why it sent the mailer.

Cron is working perfectly, the mailer queue gets processed like clockwork.

I will adjust those "Must be In state" setting - somehow they always worked in the previous version.
I migrated all the CB settings during last upgrade and manually checked every single one (reams of printouts!).
Will see if the problem goes away, Thanks!