After looking at your Super Seven outputs, the situation is as I suspected initially: a high amount of accelerated traffic on both gateways is saturating individual SND/IRQ cores. Recommend an 8/8 split on both gateways. To allocate more than one CPU to a NIC you need to enable Multi-Queue, would recommend enabling it on the eth1-04 interface on FW1, and the eth1-01 interface on FW2 for starters. When making these adjustments, adjust your CoreXL split first then reboot, then enable Multi-Queue on the recommended interfaces and reboot again. Do not attempt to adjust the split and enable Multi-Queue all in one go, as that will cause further problems.
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