Slow transfer between shares

My Cloud EX4. Drives in iSCSI config.
When I copy files from one share to another (different volumes) using Windows Explorer my speed varies from 0MB to only 6MB. That’s annoying when you have to transfer almost 2TB of data. Is there any way to speed up the process?
Thanks a million for any help.

My Cloud X4? Do you mean My Cloud EX4?

If so you may want to see the dedicated EX4 subforum where people more knowledgeable may be able to assist. This subforum (My Cloud) is generally for the single bay/single drive My Cloud units.