have you encountered the problem when you have two accounts that sharing the same phone number?
I think it is common problem, not for a designated account. When two PayPal accounts was added the same phone number, the phone number of the other one account will turn to unconfirmed if you confirm one of them.
Assuming there are two accounts, PayPal A and PayPal B, they all added the same phone number. After adding that to PayPal B, the PayPal A will need to be confirmed the phone number once you enter account. And, after confirming PayPal A, when you entered the PayPal B, you will be asked again to confirm the same phone number. endless loop.
The PayPal A and PayPal B are only sharing the same phone number, other infos are different.
Talked with PayPal's support, they said PayPal doesn't allow you to link a phone number with two different accounts simultaneously. If that is being added to a new account, then status of phone number will turn to UNCONFIRMED automatically.