MAC-address of physical interface where only a HB-VLAN is assigned seen in Wireshark for user-traffic

During troubleshooting in Wireshark I noticed that the destination MAC-address of an incoming packet is the one of physical interface 1.1, whereas the source MAC-address of the same packet in the outgoing context is the one of the correct VLAN.

 

For your information:

 

• it's running on 11.5.4 HF2
• 1.1 & 1.2 as a LACP-Trunk with just one VLAN for heartbeat, sync and mirroring
• 1.3 - 1.6 as a LACP-Trunk with all required user VLANs
• we are also using Route Domains

Now the question, is this somehow normal? Where does this come from and what does this mean? How can I further analyze this or do you need any more details?

 

Thank you!

 

Ciao Stefan :)