10gbe transfers suddenly get super slow R630 H730

hello everyone.

I have a dell R630 windows 2022 server

2TB SSD drives on Raid1

Daughters card with 2x 1gb and 2x 10gb RJ45 ports (intel)

When I transfer a large 100tb file to another server over the 10gbe network I get around 600gb/s transfer speed.

ETA will be around 3minutes.

As the transfer goes on, windows memory usage go up and I found out that consistently when the RAM usage reaches 50% the transfer speeds change to about 30mb/s.

I tried different hard drives, network card, 

nothing seems to solve this.

Any ideas?

thank you