Please provide more detailed info on the problem. What RouterOS version and wireless package you had were this all was working fine?In rc26, and it has been in CAPsMAN configuration, from the DHCP Server, which is activated in the other RB, has been confirmed a phenomenon in which the IP address is not passed.
Moreover, instead of immediately occur, but after the elapse of a few hours if you are using.
It has not been output, especially something like anxious to log.
If you have enabled local forwarding, it seems this phenomenon is likely to occur.
What setup you have on the CAPsMAN and the CAP?
Please send the support output files and also information how to reproduce this problem to support@mikrotik.com