RELATED field not shown in GUI after export, delete and import a contact

Describe the bug

I have exported a test contact with some "RELATED" Information.

The export looks as follows:
BEGIN:VCARD
VERSION:3.0
PRODID:-//Sabre//Sabre VObject 4.5.6//EN
UID:7e89a8ca-1aaf-4ee5-afeb-f458ac785fa8
REV;VALUE=DATE-TIME:20260312T135102Z
FN:test
NOTE:
ADR;TYPE=HOME:;;;;;;
EMAIL;TYPE=HOME:
TEL;TYPE=HOME,VOICE:
RELATED;TYPE=SPOUSE:Test Partner
RELATED;TYPE=CHILD:Test Kind
RELATED;TYPE=CHILD:Test Kind 2
END:VCARD

I deleted the contact in the address book.
After importing it back, the RELATED information is not display in the GUI anymore.

I'm also not able to add "RELATED" fields to existing contacts.

Steps to reproduce

As described above.
Create a new contact, add some "RELATED" fields like child.
Export that contact.
Delete that contact.
Import the contact from the exported VCF file.

Expected behavior

The "RELATED" fields should be visible in the GUI.

Actual behavior

The "RELATED" fields are not visible.
But they are still in the export, if I export the contact again.

Contact version

8.4.1

Operating system

Nextcloud AIO 12.8.0

PHP engine version

PHP 8.3

Web server

Apache (supported)

Database

PostgreSQL

Additional info

Maybe it would be usefull to have an option to display fields which are not interpreted, so that you know that there is some more information stored with this contact.

Reproduce the export, delete, and import flow for a contact containing RELATED fields, then trace how the imported contact is presented in the GUI. Check both the existing-contact editing path and the import path; done means RELATED entries are visible and can be added while remaining preserved on re-export.