ASUS RP-AC56 1200mbit extender completely not working in AP mode?

Hi All.

I purchased two RP-AC56 extenders to use in AP mode in my house (4 floors, basement included).

Here is the setup:
- All rooms have Gigabit ethernet outlets, all wired through the house to a patch-panel in the basement.
- Using CAT6 cables only.
- Basement: Asus RT-AC3200 router
- Floor 1: Installed RP-AC56 here, 1gbit lan connection. Using AP mode.
- Floor 2: Installed second RP-AC56 here, 1gbit lan connection. Using AP mode.
- Floor 3: Asus RP-AC52 in AP-mode (bad thing with...

ASUS RP-AC56 1200mbit extender completely not working in AP mode?