AP keeps deconnecting clients and high retry rates

Hello,

We have bought and installed 5 AP in our big house (for our company), made of strong walls.

• WAX214v2 (AX1800) (dinner room 1 floor 0)
• WAX214 (AX1800) (kitchen)
• WAX214 (AX1800) (bedroom 1)
• WAX610Y (AX1800) (outside)
• WAX214v2 (AX1800) (dinner room 2 floor 1)

We are facing many disconnections from the AP, experiencing very bad Wifi performances, and I can see a high rate of retries on clients.

What we have done so far to improve the situation :

• Tune the channels to totally erase the overlapping
• Enable fast roaming
• Separate 2.4ghz and 5ghz
• Reduce power when it is needed

Everything looks better know when looking at with "LinSSID" and "wavemon" tools.

But we are still facing the same issues.

Question 1 : what can we do next please to improve the situation ? (I can also share some logs if needed)

Question 2 : why is there less available 5ghz channels in WAX214v1 compared to v2 ?

Thanks a lot.