That's because of the speed limit of the port in the telecom room. Is one of you 1m, three of you or 1M? Unicom is the account speed limit, the port is not limited, and it can be superimposed to 8M at most. You can explain the situation to the telecom and open the 3M port.

If you are a 3M port, the switch supports VLAN function to reduce packet loss, or it may be the quality problem of your switch and the forwarding is too slow.