I am running CalManager 4.3(2) and we are having the following issue. Please see attached picture for basic layout.
Is the gatekeeper used as a WAN router between site A & site B? What is the codecs you are using over the WAN?
Did you check MoH is working fine on CCM A ?
What you expect when you put on hold? Since you do not have any MoH, silence?
And when you said hold fails, did you mean to say call fails?
Can you try enabling MoH Service on ccm, make sure they have G729 Codec enabled
Also, to take the gatekeepers out of the equation, I built an ICT between CCM A and CCM B. I am getting the same call behavior while routing over it as I was when routing through the gatekeeper.