gateway monitoring - RTTd bad

[Tubs]

Hello,

I noticed bad RTTd values in my local network,

Some days ago, I changed my network configuration. Two networks that before were directly connected to the OPNsense box now are getting handled by a L3 switch. Between OPNsense and L3 switch I added a "transport network", connected directly from nic to nic with a 50 cm cable. I added a static route between both devices. I am not using VLAN or LAGG on the OPNsense 20.1.1 box for this connection. But the RTTd values from gateway monitoring are worse in comparison to the values of my WAN connections.

Any idea what could be wrong?
Or could it be related to the way the monitoring is measuring?