HPE Gen10 DL380 won't connect without static ARP (Windows/Cisco networking)

Hello,

Got a head scratcher here that started a few days ago and I can't figure it out.

I have a physical Gen10 DL380 running Windows Server 2019, with a static IP/DNS. If I don't assign a static ARP entry to the gateway MAC of the Cisco core within Server 2019, it doesn't work.

Occasionally, I can flush the ARP table on both Windows and the core and it works..... for like 10 minutes before dying and requiring the static ARP. The drivers for the HPE NIC are already up to date - HP Ethernet 1Gb 4-port 331i Adapter and VMQ was never enabled. Server 2019 up to date as well.

Any suggestions?