Duplicate non-linked contacts + Contacts not showing up

[xaltsc]

Hey (and Happy New Year),

I'm using DAVX^5 4.4.4-ose (404040002) on a Google Pixel 9 Pro on Android 15 with Google Contacts (com.google.android.contacts) 4.45.31.967816832, Google Phone (...dialer) 156.-.705347550-pixel2024, Google Messages ( ....apps.messaging) version messages.android_20241120_00_RC07.phone_dynamic.

I have two issues that maybe are related, and probably aren't DAVx^5's fault, but I don't know where else to ask and haven't found anything on elsewhere.

My setup is that I have 2 WebDAV Server, only one with which I sync Contacts, and I have several address books on that server. I have a Google Account, but I do not use it for contacts.

1. While all synched contacts show up in Contacts, they don't always show in Messages. Some numbers show as unknown, even though the contact exists. When I click on a number, Messages provides me with the option of creating the contact.
2. I also have WhatsApp and Meet contacts synched on my phone. Sometimes, they are correctly linked to the CardDAV entry, other times not, and often, the contact in other apps is overshadowed by it.

Is there a way to force linking several contacts pointing to the same person ?

I also have two other less important issues:

1. No app seem to respect the display name field or surname field.
2. I though vCARD 4 allowed to set pronouns (and maybe I can set gender accord there as well ?). Is there a way to use this ?

[xaltsc]

Note that disabling synchronisation -> synchronising -> reenabling synchronisation (with some cache clearing) seem to make Messages aware of the contact again.

[devvv4ever]

Android has a built-in soft-merging algorithm for contacts. So it should detect duplicate contacts from the raw source ("raw_contact") of the accounts and merge it into one for the user displayed and visible contact that can have multiple sources. This algorithm is not very documented however and I'm not sure how this linking actually works. I know this is not the answer you're hoping for but just an addition.