Activity tab shows changes of persons who didn't do them

Problem: Activity tab shows changes of persons who didn't do them. I spoke with involved people and we could verify, that they didn't do particular changes (e.g. they weren't even at a Computer when changes were made).

Activity App version: 2.15.0

Steps to reproduce

I don't know how to reproduce this phenomenon.

Expected behaviour

Activities should have the correct owner.

Actual behaviour

Sometimes activity tab shows changes from people, who didn't do them.

Server configuration

Operating system: Ubuntu

Web server: nginx

Database: MariaDb

PHP version: 7.4.30

Nextcloud version: 23.0.9

Where did you install Nextcloud from: Payed hosting by pixelx.de

Signing status: (I dont know what you need to know here)

Result of https://..../index.php/settings/integrity/failed

No errors have been found.

List of activated apps:
Calendar 3.5.0
Contacts 4.2.1
Tasks 0.14.4
Accessibility 1.9.0
Activity 2.15.0
Circles 23.1.2
Deck 1.6.3
Deleted files 1.13.0
Federation 1.13.0
File sharing 1.15.0
First run wizard 2.12.0
Log Reader 2.8.0
Monitoring 1.13.0
Notes 4.5.1
Notifications 2.11.2
Password policy 1.13.0
PDF viewer 2.4.0
Privacy 1.7.0
Right click 1.2.0
Talk 13.0.9
Temporary files lock 20.1.0
Text 3.4.1
Theming 1.14.0
Update notification 1.13.0
Versions 1.16.0

Nextcloud configuration:

I dont have access to Nextcloud config file due to payed hosting.

Are you using an external user-backend, if yes which one: No.

Client configuration

Browser: Chromium

Operating system: Ubuntu

Logs

Nextcloud log (data/nextcloud.log)

I dont have access to the log file.

Browser log

Browser log is full of deprecation notices, but no errors. I can paste it, if required.

No source files, tests, reproduction steps, or logs are identified in the report. Start by determining how the Activity app attributes changes and obtain server logs or a reproducible case; done means the activity owner reliably matches the person who made the change, with a regression test if the cause can be isolated.