Hello,
I am running the latest version (12.9.8), when deleting a subdomain, does not delete the AAAA DNS record for the domain, then recreating the same subdomain, causes duplicate AAAA record for the domain.
Edit: I found more "bugs" today while working on a server with only Email role installed, all the subdomains I created for a domain (another server with App and DP roles installed) exist in mail server. for example, I have created example.com in CP, app and db are on one server, email for example.com is on another server, I created an email info@example.com, then tried creating some subdomains (testing.example.com) for example.com, then I removed the subdomain, but today I saw folders for those subdomains in my mail server.