Hi Matthias, that means you have DoS Protect enabled on BD8k to apply an ACL if more than 3500 pps reaches the switch CPU.
For some reason this might be caused by X440 side that's connected to BD8k port 4:1 (based on the log provided).
Is there anything connected to the new switch like other switches, PCs, phones, etc?
Did you change the switch configuration or it's using default configuration?