I have had this ongoing issue with the TL-SG2210MP limiting throughput. 

I have a Unifi Gigabeam (AP) wired to port 7. The second Unifi Gigabeam (Client) is wired to my router. Initially throughput is near 900Mbps up / down but at some point for unknown reasons, it will drop and lock to around 70Mbps up/down.

I have the ability to test the speed between the two Gigabeams and when this issue occurs, the throughput between the Gigabeams is still maxed out at gigabit speed. I can also test between the Gigabeam (AP) and my PC connected to my router and speeds are full.  So the issue is traced back to the TL-SG2210MP. 

I can move the ethernet cable for the Gigabeam (AP) from the port 7 to port 8 and the issue clears up immediately,  but at some point the issue will resurface on that port. Moving it back to 7 clears it up again. 

Any recommendations?  This issue did not start happening until we put the TL-SG2210MP in place. Prior to that we had a different switch that worked without issue.