Access point not working in 1 area of building

[JeremyO]

Please delete

[Stefan_Sleik]

Hi,
When you have 4 Aps with the same Configuration. So you can switch 2 of them. Moves the failure with the AP? 
If Yes: Configuration issue on W-Lan.
If No: Configuration or Hadwareissue on the Backbone LAN.
Tagging on the Lan-Ports is okay?

regards
Stefan