Category issue
Assigning a contact to a category throws out the previously contact from the category it was assigned to. Ex. Assign contact A to Category "Service" Assign contact B to Category "Purchase" Result: Contact A is moved to Un-assigned.
If you delete Contact A and import it with the Category added to it before. Result: Contact B is moved to un-assigned.
Thunderbird 68.4.2 CardBook ver. 43.8
Erik Lennartsson