External Ports 2 x Thunderbolt 3 port (type C) 1 x 5 pin TB header 2 x DisplayPort input ports;Specifications Chipset Intel Thunderbolt 3 controller Interface PCIe 30 x4 Capabilities Supports Display Port 12 with max 4K x 2K @60/24 Hz Accessories 1 x TB header cable;9/9/The output is going via a thunderbolt 3 hub, (CalDigit TS3) On investigation the current thunderbolt driver installed in the laptop appears to be relatively old, driver version dated , updating this driver seems a good place to start to fix this issue
Sonnet Allegro Usb C Pcie Dual Port Card Epowermac