What's your upstream port configuration look like? Pair of switches that are cross connected with same VLANs?
Based on the vSwitch config you would need an 802.1q trunk with the management VLAN configured as the native VLAN on the trunk, and VLAN 50 as an allowed VLAN. I would double check that VLAN 50 is allowed on VMNIC7 (since you know it works on 0). Do some pings and check the MAC address table on the upstream switch, make sure the vmkernel MACs show up where you expect them to.
Otherwise should work. You can tail -f /var/vmkernel.log during a vmotion to see why it is failing. This will probably only tell you IP xxx.xxx.xxx.xxx. couldn't talk to IP xxx.xxx.xxx.xxx.