Custom email/phone labels not working

Describe the bug

Setting custom labels for a phone number and email address does not work currently. While it is possible (after retries) to type in and select the label, after saving and reloading the default "Private" appears in the UI. Checking with a different app (DAVx5 -> Fossify Contatcs) those custom labels are set. Editing the contact again and selecting "work" instead of "private" (which already is wrong at this place) removes the number/email completely.

Steps to reproduce

1. Create phone number/email with custom label
2. save contact
3. reload page

Plus for the real mess:

1. edit contact again
2. select work instead of private as label
   --> the phone number has been removed completely.

Expected behavior

Contacts with custom labels are displayed correctly.

Actual behavior

See bug description

Contact version

8.4.5

Operating system

AIO container

PHP engine version

None

Web server

None

Database

None

Additional info

No response

Start by reproducing the custom-label steps in the issue: create a phone number or email with a custom label, save, reload, and edit it again. Trace the save and reload behavior for contact labels; done means custom labels display correctly after reload and changing the label does not remove the contact value.