solved it, need to activate Local Forwarding in CAPs Datapath Configuration in the CAPsMAN but no clue why.
I watched Mikrotik CAPsMAN Setup Tutorial - YouTube again again. At 4:13 he mentioned Local Forwarding and Connecting all CAPs to the MikroTik CAPsMAN - YouTube said once there is CAP to CAPsMAN data traffic. So slowly the idea matured in my mind that this may helps me, in particular as this kind of communication is mentioned in Manual:CAPsMAN - MikroTik Wiki mentioned it as well that there are these kinds of modes.
Unfortunately, it does not say why Manager Forwarding Mode requires particular DHCP setting. Can anyone explain?