09-20-2018 09:48 AM
For the benefit of anyone who has been keeping tabs on this thread, and for anyone who happens across it in future having had a similar issue, I can report that we have managed to get to a state where performance seems reliably strong.
I've been very cautious about declaring this as resolved, as throughout this process I've had false dawns and wanted to make sure the APs were monitored thoroughly for a long period to ensure they were behaving as required.
The solution for us was to tweak the 'Min transmit power' and 'Max transmit power' of our VC's ARM settings. These are now set to 3 and 18 respectively. Previously they were set to 18 and Max. Our networking provider recommended lowering the settings, and through some trial and error, we came to the current settings, which are now working for us.
Again, thank you to everyone who offered help and advice above!