From the beginning my phone has some random wifi issues, I am at the point that I am sure this is not related to the network itself, since I tried two different wifi-routers and all their settings. And I also saw the issue once at the office, where  a co-worker also with an S23 does not have these issues.

The issues are:
- random disconnects followed by a reconnect within 3-4 seconds. My connection can last an hour, but sometimes it disconnects after two 2 minutes.
- when entering a known wifi network and you expect it would switch from LTE/4g/5g to wifi, it does not. I go to the wifi connection page and there is just a text saying "enabling wifi" or "scanning for networks" - I waited as long as 15 minutes and does not come up with any networks, the phone's wifi just seems to hang in a sleep mode. When I manually turn wifi off and on again on my phone, it immediatly connects and shows the list of networks.

I am now testing with a clean factory-reset phone, where I just configured the wifi network, no other software or configuration. The problem is, it is not always 100% reproducable.
When I go to the shop, trying to convince them it is a hardware problem. They connect my phone to the shops wifi and claim it works fine.
So, for now they refused to take it back.... Anyone out there with the same problem or any suggestions?
I will probably just go back to the shop again and hope there is another person at the desk, that just believes me on my word?