@Sunshine 

Hi,

I don't know whether the wired (9pcs) connection works as it should, but most likely it's better than the 2.4GHz. (23-25pcs)It seems to disconnect partly and the internet is off. It seems to be a kind of database trouble where the 2.4GHz is the worst.

The 5GHz (5-10pcs) also disconnect with the same problem...but slightly less.

I have also tried to change channels and a lot more to fix, bit by bit but the only thing that works is to restore the old firmware.

  @Sunshine At this point I have also tried to upgrade to a firmware inbetween (C3150(EU)_V2_220330), suggested by the support.se@tp-link.com.

It was not a full success.
 

"I did dare to try the  C3150(EU)_V2_220330 and got some errors - see attachements. After a while the router came up properly and found wifi items, but the throughput is not so good.

There is also random errors and AM/PM on the parental controls - and the history in parental control is gone. Speedtest does not work.

I'm going back to the the C3150(EU)_V2_170927 until you come up with a solution."