I can see udld table between c6500s across samsumg L2 switche. like CDP.
The Cisco layer-2 control protocols VTP, DTP, CDP, PAgP and UDLD use all the same destination multicast MAC-address: 01-00-0C-CC-CC-CC. The frames are send untagged on trunks, non-Cisco switches usually treat them as "normal" layer-2 multicast.
So the question is, why did the Samsung switch stop to forward those frames in its native VLAN after you changed the VLAN.
Is the Samsung switch running a rapid spanning-tree mode? If it's non-rapid, maybe the configurattion change made the port to run through Learning and Listening states for 30 seconds (I assume those STP states are port-based, not per-VLAN on Samsung switches)?