Everyone - We are working on improvements for ARM devices wireless performance within 6.42rc version. Such fixes/improvements can not be backported to older versions and will be included in RouterOS current versions only starting from 6.42 release.
venthyl - I just tested the same and it worked. Ran print OID command, took random OID from multicore system and this snmpget command worked just fine for me = “snmpget -v2c -c public 192.168.88.2 .1.3.6.1.2.1.25.3.3.1.2.32”.
Spirch - Most likely you have, for example, DHCP servers on both devices which messes up addressing or something like that. I recommend that you send supout files to support@mikrotik.com. As for reboot - do you power hAP from cAP ac PoE out interface?