To solve this question, you'd better check the partition of your HDD in advance. The Windows built-in tool CHKDSK can help you to do this operation. if you are not familiar with the command prompt, you can also check partition and fix errors with third party software. if there has bad sectors on your HDD, fix it and you can use your HDD normally。
Nope, my SSD is brand new I've ran a CHKDSK command on it no issues, the problem is Windows Explorers file transfer this issue has preceded since Windows 8 from what I've researched and still exists in Windows 10, you would think Microsoft would've fixed this issue by now but they haven't yet. Here is what happens, Windows explorer will transfer small files just fine but as soon as you transfer multitudes of files like i.e. i can transfer 1-4 files at a time but once in a while, If i do more than that the transfer speed suddenly drops down and halts its transfer. Like you i thought it was a possoble failing or corrupted drive but it wasn't, i did some research and found multiple people experiencing the same issue since Windows 8, so I tried a third party file explorer called One Commander and the transfers are just fine even for big/multiple files.