Traffic to default route brings down clusterbox networking

If I try to generate any significant network traffic over the cluster box firewall, the cluster box latency increases to over 1000ms and then the cluster box drops off the network until the command on the blade times out. This makes the OpenWRT part of the cluster box unusable.

Alternatively if I scp a file from the cluster box to the blade the network stays normal, so the problem occurs when the traffic is destined to the cluster box default gateway.

firmware: mixtile-cluster-box-v0.0.3-20240506 / LuCI openwrt-23.05