@megavolt has suggested that my problem was an hardware issue:
For a few days now, the problem has disappeared as quickly as it appeared. On closing the lid, the touchpad etc. are disabled as intended and no subsystem/hw/… tries to enable them (this has led to annoying behavior, see linked topic). As long as there is no self-healing hardware, I assume that it is not a hardware problem. By Manjaro distributed and updated firmware could be possible, but I don’t have the knowledge to verify this.
Where is the Manjaro issue tracking for finding known bugs or entering and tracking new bugs?
Maybe check the dates when firmware has been updated:
grep "linux-firmware" /var/log/pacman.log
When problems occur on updates, then report it here #announcements at the correct date and branch. There is no specific bug tracker for Manjaro. Or you can also send an email to the packager, if you can prove that there is a problem.
The firmware update dates fit reasonably well. I am a bit surprised that I worked with a laggy mouse for over half a month. But it may possible. Thank you.