Hello,
I am using this device in a tower to only download 1 cable (fiber) but a few days ago the CPU went up to 100% and there is no way to go down, I have a maximum traffic of 150mb, and I have 7 of the 8 PoE ports in use.
From my testing you should be able to push ~300Mbit/s or so over the CPU, a firewall rule/nat would push the CPU to 100%, it is a switch after all.
Is hardware acceleration enabled on the bride interfaces?
Export your config and post it in the code tags.
Make sure you use hide-sensitive to hide any passwords and stuff.
/export hide-sensitive