I have a couple of hAP ac² and 3 cAP ac's. With identical radio settings, the cAP ac's ALWAYS selects 5200 MHz as channel when channel selection is set to auto. The hAP ac²'s will happily go to some of the higher frequency channels and initiate DFS, wait for 10 minutes before determining that the channel is clear and then start transmitting. Regulatory domain is set to "Denmark" for all devices.
Even if I place the cAP ac's next to each other and boot them in sequence waiting for the first one to do channel selection before I boot the next one, all 3 of them will choose 5200 MHz. This happens even if the hAP ac²'s are powered off so that the channel previously occupied by the hAP ac²'s become available to the cAP ac's.
This is only a problem on the 5 GHz band. For 2.5 GHz the cAP ac's will find 3 different channels.
This puzzles me, since AFAIK the hAP ac²'s and cAP ac's are using the same wireless chipset (IPQ4019). I'm not using CAPS/CAPsMAN on any of these devices.
Why is the behaviour different between the hAP ac² and cAP ac, and is there any hints to optimizing auto channel selection on the cAP ac, so that they choose different channels?

Forgot to mention: I've tried tried this on both 6.42.3 and 6.42.2. No difference in behavior between those versions.