I have recently managed to get a USB4 thunderbolt device to cause a Freeze-then-Reboot (FTR).
On subsequent reboot the S5_RESET_STATUS is the “…sync flood…” one.
So, this proves a USB4 / Thunderbolt device can cause a “…sync flood…”.
I have a BE200, but when I place it in a USB4 enclosure, it does not work at all. Does not appear as anything on the FW16 and does not crash the FW16. The same BE200 works fine in an ARM board.
Would you be able to repeat your test with the BE200 that causes the reboot, and then tell me what the S5_RESET_STATUS is after the reboot.
On recent Linux kernels, 6.18.x you might see a message like this, after the reboot:
Previous system reset reason [0x08000800]: an uncorrected error caused a data fabric sync flood event
This will then confirm that the BE200 is causing a “sync flood”.
This might then coax FW and AMD to try to fix the “sync flood” / random reboot problems with the FW16 AMD 7840HS and others.