I also have a High Collision status on both Wifi0 and Wifi1.
From looking at previous topics concerning this I have disabled 2.4Ghz on both 1, 2, and 5.5. I have also enabled Band Steering for 2.4Ghz to 5Ghz on a cloned 2.4Ghz radion profile for the 802.11g/n radio.
The Show ACSP command returns that Wifi0 is on channel 6 with Tx power of 6 and Wifi1 is on Channel 149 with Tx power of 12.
I have only about 5 clients on this AP at the moment, but want to make sure this is something that should be fixed to help get the most out of the AP230 that I have.
A good place to start looking is the Troubleshooting tab in the Dashboard.
If you are running voice services then it could be an issue.
If you are just running data services then I would recommend testing the throughput using an iPerf v3 server.
I have a number of wireless networks up supporting hundreds of users without an issue and it is not uncommon to have wifi0 and wifi1 reporting high collisions.
The "wifi1 interface client Tx retry rate alarm threshold:40 current:69" warning means that your access point's 5 GHz radio is struggling to get access to the medium to transmit. Can you change the 5 GHz radio's channel to another channel that is not so highly utilised? Another thing to try is to disable the DFS channels (this is done in the 5 GHz radio profile) as this may be causing your issue.
If you run the show acsp neighbor command on the affected access point what do you see?
When you completed the wireless site survey for your high density deployment what transmit power did you have the access point's 5 GHz radio set to? 14 or 17 dBm? Have you placed access points in corridors or other open plan areas where the signal can propagate over other access points?