Steps to reproduce:{}

1. Start with Zabbix 5.0
2. Create a couple of hosts, give them ZBX interface.
3. Create a template, link it to the hosts
4. Create couple of items of HTTP agent type
5. ???
6. Switch some items to type Calculated or type Dependent
7. Add another interface (SNMP)
8. Swith all items that are still HTTP agent to new interface
9. Upgrade from Zabbix 5.0 to Zabbix 7.0
10. Try to delete ZBX interface

Result:
Original ZBX interface cannot be deleted.
Database query confirms calculated (type=15) and dependent (type=18) items "use" it.

Also database query confirms this affects all hosts that link affected templates same way.

Also database query found more affected templates/items - all originally HTTP Agent.

I don't know how exactly corrupted items happened, "steps to reproduce" is my guess.

Anyway, this report is about upgrade process, either 5->6 or 6->7, not cleaning this mess up.

I hope this helps you find the bug(s). Thank you.