Importing pcap with 802.1q encapsulation results in no data

[jraber]

Steps to reproduce:

1. Setup a SPAN session a Cisco switch with an 802.1q trunk as the source and with the destination option 'encapsulation replicate'

interface GigabitEthernet1/0/1
 description A Trunk Port
 switchport mode trunk
end

monitor session 1 source interface Gi1/0/1
monitor session 1 destination interface Gi1/0/2 encapsulation replicate

2. Use dumpcap to capture that data.
3. Load that pcap in grassmarlin and notice that either no or very few hosts are listed. The only hosts listed are those that passed unencapsulated data (eg for spanning tree or CDP)