exported vCard phone number with ; or , is re-imported incorrect

When a phone (or fax) number field consits of ; or , (used for pause and wait) it can be exported correct to a .vcf
However, to import the same file back to contacts creates a wrong entry.

Example:
Fax work: 205246;;,;
vCard export: TEL;TYPE="WORK,FAX":205246\;\;\,\; (what is correct according to the RFC)

reimport into contacts produces:
Fax work: 205246\;\;\,\;

Looks to me the parsing at import does not work correct

BTW: when synchronising with iOS, same issue happens when synching back from iPhone to NextCloud (this time, it's not an Apple ... feature ;-) )
......

To Reproduce
create a new contacts entry
enter a phone number and add ; and/or , to it
export to .vcf
open the exported .vcf and delete the UID identifier line; save it
import it into contacts
check the phone field

Expected behavior
phone number should show up like entered before

Actual behavior
the \ of the .vcf file are not parsed correct

Server configuration

Operating system: RaspBerry Buster

Nextcloud version: NextCloudPi 16.0.5

Contacts version: 3.16

Updated from an older Nextcloud or fresh install:
Updated

Start with the contacts import workflow described in the reproduction steps and compare its handling of escaped semicolons and commas with the exported .vcf example. Verify the behavior using a phone or fax number containing pauses or waits; done means importing the exported file restores the original number without displaying backslashes.