This can happen on any device and version before RouterOS is fully booted, you just have to wait a minute and try again...
Many hours later and still the same, so > No that is not the problem sadly.
I have a hAP AC2 that is operating as a wAP under Capsman control. I have upgraded it sequentially. It is working fine with 7.23.1. No VLANs however.
Thanks!
Just to be clear: 7.23.1 now works on my cAPs now but it was getting there that was bumpy. This was the same for some of the latest 7.22.x and for the 7.23 update. Have never been a problem before running and updating for years without config change. Main problem: After upgrade all wifi interfaces on cAPs are disabled and can not be enabled without applying the fix i mentioned in my first post (going back to "long term" and then reapplying"stable")
The Winbox connection failure to a single wAP AC must be something different and as long as i can connect with RoMON im ok with that. This AP has been my vacation road warrior so it probably needs a clean wipe... 
Since upgrading from 7.21.x to 7.23.1 I'm seeing failures of my CAPs to connect to CAPsMAN and subsequently a short down/up on all interfaces for the CAP which just logged a loss of connectivity to CAPsMAN.
I am running three cAPGi-5HaxD2HaxD, one of which is CAPsMAN for the other two.
The configuration was unchanged during upgrade, both OS and RouterBOARD upgrades went without issue and are reporting the new version. All devices are running the same software images (routeros and wifi-qcom) and there were no other changes to the network.
The flapping appeared with the upgrade and I haven't found any reason as of yet.
Any help is appreciated, it is kind of flooding my monitoring.
At this point I am considering downgrading back to 7.21.x, but given the security implications I'd rather solve the real problem instead of trying to go back which might not even help.
What is output of
interface/wifi/capsman/print
on CAPsMAN device and output of
interface/wifi/cap/print
on other devices?
Nobody can help without that simple piece of information - which does not contain sensitive data in it.
P. S. I experienced ARP-related problems with 7.23 and 7.23.1, which got resolved by updating to 7.24rc. Your problem might not have any relation to this, but yet it might...
Version 7.23.2 has been released:
This happened to me, very strange
Both dhcp server and client on the bridge?
Config would be helpful:
/ip export
I used to leave a DHCP-Client on the bridge as a "canary" (No DNS, no NTP, and no Default-Route)
This was akin to "/ip dhcp-server alert", but with the advantage(IMO) of facilitating access to whatever delivered the address for correct configuration.
Historically, Routeros would not "lease to self" on bridge
This behaviour changed recently, so i moved my configs to use "/ip dhcp-server alert" instead