Copy speed reducs to zero from one drive to another

[druvanil]

Im using 2 internal HDD both WD green. One is 2tb(primary with win10) and another one is 4tb.
My 4Tb hdd has two partition drives of 2.5TB and 1TB.
Now the 2.5TB partition seems to be working fine . But when i try to copy any movie from 1Tb drive to any pendrive or any other drive my copy speed simultaneously decreases to Zero.
At the start of the copy the speed is around 40/50mb/s for drive and 30/40 mb/s for a pendrive..but within 15/20 seconds the speed gets reduced to zero.
I tried checking crystaldisk/WD diagnostic apps both shows my hdd is okay.
Where could be the problem ?

 

[yuichi03]

Hmm, I'm aware of what's happening here as I've experienced this problem before but it can be fixed most of the time by rebooting. The drives you're using, WD Green, is a drive that runs slower than usual drives like blues, much more quieter, and less power hungry. Thus, slow/read write speed on this drive is normal, but when you mentioned it drops to 0mb/s, then it's not normal, and it's also another reason this thread caught my attention. Is it possible if you upload a screenshot here? On the meantime, you can try defragging your drive those drives.