user search does not search family name, finds entries that don't match

I want to write to user that has P in the Family name,
I press 'P' in the text field

For the Chats results section it searches both Name and Family Name

For Users (that I have not yet chatted with):
users with P in surnames are not shown for example John Pocot
users with P in first names are shown correctly
additional user that does not have P is displayed "k. Romak Kudlek"

The text parts i blurred did not have P

Diagnosis report

Application config

{
  "launchAtStartup": false,
  "theme": "default",
  "systemTitleBar": true,
  "monochromeTrayIcon": false,
  "zoomFactor": 1,
  "playSoundChat": "respect-dnd",
  "playSoundCall": "respect-dnd",
  "enableCallbox": "respect-dnd",
  "secondarySpeaker": false,
  "secondarySpeakerDevice": null,
  "trustedFingerprints": []
}

Start by reproducing the user search in Nextcloud Talk with a surname and a first name, comparing the Users results with the Chats results. Trace the server-side search entry point used for users and inspect how name fields and matching results are handled. Done means surname matches are returned and unrelated users are excluded.