OpenVPN Bridge on pfsense: once LAN pings clients, connectivity breaks

[deassain]

So I'm using a pfsense openvpn to bridge my LAN segment so VPN users can access the servers.

The problem I'm having now is that I can establish a connection, I can ping the LAN server from the VPN, but as soon as I ping the client from the LAN server, there is no connectivity anymore between both parties.

So:

connect from the VPN client to the LAN => works
ping the LAN from the VPN client => works
access server from the VPN (ssh, ftp,…) => works
ping client from server => doesn't work
ping LAN from the VPN client => doesn't work anymore
My bridge has em1 and ovpns1 bridged. I noted with tcpdump that ICMP is reaching the bridge between LAN and the VPN segment. But it's not put onto the em1 interface for some reason.

My pfsense is running on an ESXi host with the vSwitch port enabled in promiscious mode. Firewall rules allow in and outbound traffic regardless origin or destination.

Anyone any idea how I can fix this?