Question on multicast

Good morning all,

I'm trying to figure out a multicast issues that's apparently plagued my organization since before I arrived a couple of years ago. We have a vlan that we use specifically for imaging but when trying to image at another location the multicast traffic is getting refused. One of our managers believes that our routers are denying the multicast traffic.

The way our network is setup:

We have a core switch where the VLANs reside. The different buildings all connect back to the core and are trunked. We have various Cisco 2900 series routers at each building that connect to one of the ports of the building switches that only routes phone traffic from what I understand (Those are the only routes I see on the routers and I think they're only used as a failover incase we lose internet connection and then it switches to landline). The only routes I see on those routers are for the phone vlan.

When our hardware guys try to image a computer via multicast the traffic seems to go through to a certain point and then stops. As a test the router was disconnected and they tried imaging a computer again and lo and behold it worked. However, this doesn't make any sense to me as none of our other vlans are routed through this router so I don't see how it would be responsible for these issues? I'm getting ready to start digging into this further but I wanted to check and see if I'm wrong about the router possibly causing the multicast traffic to drop once it receives it.