10Gb Ethernet:
"energy efficient" drops power to the 10Gb Ethernet chip to save energy. It is NOT compatible with Top Speed. In the hardware pane, set Manual, then under Duplex, set: “Full-Duplex, Flow Control” NOT “Full-Duplex, Flow Control, power efficient” to disable power saving and boost top speed.
The Mac Studio has a 10Gb Ethernet port. This 10G Ethernet port is NOT compatible with speeds slower than ONE-Gigabit Ethernet. It is also NOT compatible with cables that have fewer than all four pairs available for data.
If you have some fancy equipment at the other end of the cable, it is possible it is trying to make a 10Gb connection. A 10Gb (or 5Gb or 2.5Gb) connection is only stable when cables are excellent and fairly short (like Category-6 rated cables under 100 feet). If either of those are not true, or you have you added patch cables that are not Category-6 rated, you could be seeing it connect at a faster-than-Gigabit speed, then error out and disconnect.
The setting [√] ABV/AEV mode selected on the hardware pane of advanced Wi-Fi Ethernet OR in your Router may constrain the connection in unexpected ways that could limit overall performance. The feature is used ONLY for prioritizing “live” camera video streams over Ethernet”.