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Hello fellow TPLink'ers!
First post here but I've been browsing for a while :)
Ok, this time I search the forum but came up empty so here's the deal:

Equipment on site:
1 - EAP225-Outdoor with the latest firmware 1.2.0 Build 20180411 Rel. 63038(4555)
4 - CPE510 V2 also with the latest firmware 2.1.11 Build 20180117 Rel. 68885(4555)

Implemented scenario:
The EAP225 is broadcasting both 2.4Ghz for a couple end-users to connect to directly; and it's also broadcasting 5Ghz only for the 4 CPE510.
I'm only using 1 SSID in 2.4Ghz, and also only 1 SSID for 5Ghz.
The 4 CPE510 are operating on cliente mode. Each of them then has a switch for a couple end-users as well.

The problem:
For some reason, I force the 5Ghz to a specific channel (either 100; 112 or 136) and a few hours later, the EAP is broadcasting on channel 36 56 64 or whatever, and that causes the 4 CPE510 not to work since they only seem to work on channel 100 or above
So basically, I'm logging everyday to the EAP225 to change it's channel from whatever back to the values I need.
The end-users who use the 2.4Ghz SSID never report any problems what-so-ever! I have also never noticed any miss-configuration in the 2.4Ghz section of the network. It's always as I want it!
I am the only 5Ghz SSID in the area, but there is around 6/7 2.4Ghz SSIDs present...
I'm in Europe by the way!

The help request:
What can I do to improve this situation? What may be causing all this trouble?
The way I see it I can solve this two ways:
Either I force the EAP225 channel and it stays there where I want him to work, or
[*]I configure the 4 CPE510 to also work on a broader range of channels (which I don't see any GUI options what-so-ever)
2.1.11 Build 20180117 Rel. 68885 (4555) 2.1.11 Build 20180117 Rel. 68885 (4555) 2.1.11 Build 20180117 Rel. 68885 (4555) 2.1.11 Build 20180117 Rel. 68885 (4555) 2.1.11 Build 20180117 Rel. 68885 (4555)