T440 Error PCI1318 A fatal error was detected on a component at bus 4 device 0 function 1.

I have a T440 with Proxmox Virtualization runnig on it since 7 years.

2x RAID1 runs on PERC H730P Adapter.

It normally works like a charme. But since months the error "PCI1318 A fatal error was detected on a component at bus 4 device 0 function 1." appears in the logs. 

And sometimes the whole server stops working when rebooting. Then I have to stop and start via iDRAC. 

All firmware is updated, Proxmox is v8 (updated). How can I diagnose if the RAID controller is faulty?