Abnormal operation of several access points

[systy]

Hi,

First of all, I apologize for my bad English.
I encounter an anomaly which I don't understand the source.

Hardware:
AP: C9120AXE
WLC: 9800-L (17.3.4)

Context:
On a floor with 5 APs, 2 are giving me problems (they are not next to each other); Say AP A and AP B.

Symptoms:
AP A has no customers and AP B has customers.
If I restart AP A, some clients connect (not those of AP B) then on it (or spread to the other APs) but no more on AP B;
If I restart AP B, some clients connect to it (or spread over the other APs) but no longer to AP A;
I can't get clients on AP A and AP B at the same time (although they are not the same clients concerned).

And when I connect with my smartphone in the immediate proximity of the "faulty" AP (the first one restarted) I will connect to another AP much further away (neither on AP A nor B)...

I don't see anything strange on the WLC side.
I tried to replace an AP with a spare AP and the problem remains the same.

I don't know if my explanations are clear, I remain at your disposal if more details are needed.
Would you have an idea / a solution to this anomaly?

Thanks

[JPavonM]

The main thing you need to take into account is that every device connect to whatever AP they select based on multiple metrics from the driver (developers use different algorithms to take such decision).

First think you need to do is to check the signal quality accross the office (SNR values). Additionally, I'd recommend you to disable load balance or any forced roaming feature that could be enabled and, of course, update wireless drivers on the devices (Windows, Linux, MacOS) and test again.

HTH