@Lectron8 

Just for giggles, have you confirmed the signal strength of the active connected clients during these issues?

We need to see where they are sitting at during these issues.  This is step 1 in figuring out what is wrong.  (Besides updated controller and firmware)

Go to the client list and click on the 3 dots on the right of the list.  Check customized columns.

Check: Channel, Signal, RX, and TX, Wireless connection.

Look at what band they're sitting at and the signal level.  You will want your clients to be below -70... anything above -70 is heading to a bad connection.  You really want you clients to be in the -50 to -60 range.  Your clients need to roam between bands and APs properly.  If you have low signal on the 5ghz, thats means the client isnt roaming between bands properly.  Enabling Mini Rssi on the 5ghz will help that.  If you have low signal on the 2.4ghz, that would mean you could have a DEAD spot.  Add another AP.  

Look at your RX/TX numbers... the lower the number means more interference.  Change the channel.  

This is the quick way of checking how HAPPY your wireless clients are playing with the network.  

  @Lectron8 

When the AP drops, does POE on the switch turn off too?

Do you have meshing enabled?  If so, does this AP try to mesh on its own? (good test) 

Trying to figure out if it could be a bad cable or connector.  

  @Lectron8 

Here is what a happy 225-o to 225-o link looks like in my 5.x controller.  (BTW there is zero reason you shouldn't upgrade to the 5.x series with these devices)

My guess is you are seeing worse numbers than my 55% (-68dBm).

If your wirelessly meshed nodes are constantly loosing sync due to poor signal quality/strength or high channel noise, then they will randomly 'Isolate', 'Adopt', 'ReProvision', and that will bounce all the attached clients to other APs if they can reach them, or disconnect them if they can't.

For the 5GHz radios in your wired nodes, are you on Auto channel, or did you fix a specific channel?