Hello, I'm quite new to the bitcoin world.

I'm facing this strange issue, I'm running a Dragon Miner T1 which should run at 1TH/s.
When I log into its interface I see, in fact, that it's running at the said speed, but, when I log into the pool, I can see a quite lower speed, something around 500 - 600GH/s usually.

Do you have any hint how this might be possible?
I replaced its fans so I might think it might be an overheating issue, but I don't understand why, on the miner page, it says the right, full, speed.

I also made some tries changing difficulty - don't think it matters, but I'm also not sure what to set

Any help?
Thanks