Try switching to bbr for congestion control, and adjust the buffer sizes. The defaults are good for Gigabit but not really for higher speeds. Not near my computer right now so I can’t grab a copy of my sysctl settings, but searching Google for “Linux TCP buffer size tuning” and “Linux enable bbr” should find some useful info.
If the devices are different speeds (eg one system is 2.5Gbps but another is 1Gbps), try enabling flow control on the switch, if it’s a managed switch.