USB faulty?

[MattKier]

Hello. 
 

I have had some issues with my computer lately. 
GPU acting wierd, HDD's acting wierd and a liquid cooler taking in air for no apparent reason. 

- But right now I'm taking backups from old drives because I get new ones today. 
These drives are old. 2009/10 old. 

I'm transfering to my USB 3.0 external drive but the speed max out at 4mb/s and drops as low as 20kb/s. I remember that I had speeds above 200mb/s before. 
If I'm transfering from my internal harddrive to my boot drive - which is SSD - I get speeds of 50mb/s.
And vice versa from SSD boot drive to another internal drive.. 50mb/s 

Drivers for USB 3.0 are installed but recently I had to take my computer apart and go on a plane with it and assemble it again - twice. The first time reassembling was when the problems started.
I read somewhere that it can only transfer as fast as the drive can read the files. 
But that seems strange since I can transfer 50mb/s from one internal drive to another. But I'm a noob so what do I know. 

Can anyone say if it's because of the internal harddrive or if it's my motherboard acting up? 
Or maybe even a solution? I have 500gb to backup and with this rate it's gonna take me two whole days.

My specs just in case
Core i5-6600K 
Asus Z170-A motherboard
Asus r9 390
HyperX Fury DDR4 2133mhz 8GB
And very old harddrives - besides the SSD which is one year old. 

[Tanner779]

Try defragmenting the system,maybe that's why the speed sometimes drops..