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Maybe using Port Forwarding, 1:1 NAT rules, or NAT Exceptions could be a way around it. Just gotta make sure you've got the right network setup and routing config.
Yeah, understanding your routing config and VLAN setup will help troubleshoot this. Running a packet capture on the LAN side MX could also provide some clues.
The Netgear GS116 and TP-Link TL-SG116 are solid options worth considering, as they mention 802.1p support. If you don’t mind exploring managed switches, they can give you more control over VLANs.