seagate expansion portable

Hello, I bought a Seagate Expansion Drive (STEA 1000400) 1 TB 3 days ago. It was performing as expected up untile today. Today I noticed write speed of it has become extremely slow and inconsistent. Like it is 300-400kb for 1 second, then for 3 second it's 0kb, then again after it peaks at...

hi i bought a new Seagate 1tb hdd to harvest the sata Hdd inside and then use a 250-500gb hdd with that external case as external hard drive... my question is: is it possible to use size other than 1tb drives with that sata to usb bord? also is it possible to use other brands like toshiba or it...