Apple Device not able to connect to 1852 AP

[owen2]

I have a client using 1852 AP with version 8.5.182.

Total 10 AP with 1 as a controller to cover 3 offices across 3 levels.

users at level 2 with Mac devices ( IPAD Pro and Mac book-running  IOS 15 ) experience intermittent disconnect and connect to the wireless network at certain timing ( 8-10 AM, 2-3 PM). Funny thing, only Mac devices have this issue. Window and Android phone even wireless printer doesn't have this behavior.
Have looked through the log on the controller, not able to find the log for the cause.
tried to switch the POE switch from levels 1 and 2.
the issue still persiste.

Any advice will be appreciated. 

[Sandeep Choudhary]

can you run a debug on wlc for specific client and paste here.

debug client <mac address of failed client>

[owen2]

Can this command run on the AP controller?
The environment is not using WLC but an embedded controller in AP.

[JPavonM]

Are they running iOS 15.0? There are some connectivity issues in htat code so the recommendation is to upgrade to 15.1.

[owen2]

Yes, running 15.0
but on levels 1 and 3 there is no issue with connecting.
This is the only reason that puzzles me.