@nebulon OK, new installation tested. Fresh Ubuntu 18.04 server Virtualbox clone, then installed fresh Cloudron. Cloudron ID is exactly the same id as previous installation (d781350d-8cc0-4d73-85a6-5214430500b8)
I did not change any VirtualBox "hardware" settings. Maybe I should try again, different RAM and different HD size?
BTW, all test installations have been configured for the same domain. Dont' know if that has anything to do with creating this odd problem?
Maybe I could have avoided these problems if I had uninstalled the installed apps in the first cloudron, before I deleted it. But main problem would still be there, then maybe for others to discover.