I just ran into this problem also. The download took 8 hours to complete downloading at roughly 184MB/m. When I took the Host drive out and popped it into a Sata reader, Hard Disk Sentenal showed 282 bad sectors. Threw the drive out and put in a new drive. Image pulled down at 2.64GB/m again.
My issue was a bad drive but don’t let that account for possible other issues.