How does Bitrix Location affect the phone number in the ordering process?

Question

1C-Bitrix

When placing an order, an authorized user automatically pulls up the phone number from his profile. The phone number uses validation like: [phone]
But there is a strange bug, as soon as we select some location, the number 7 is automatically added to the phone number and it turns out that the last digit of the number is lost. Those. it turns out: [phone]
where to dig in general, at least approximately? I got lost in the study of documentation and forums - I don’t see this anywhere.