Hi,
I just tried two different Windows 10 ISO's using the Win 7 USB Tool and both completed successfully..
I can only think you may have a bad flash drive...
I would think that if it were the ISO, the problem would not happen at different percents...
You might try RUFUS as mentioned previously... Here is what your screen should look like, although the name of the ISO and flash drive will be different...
I should note that this is for a Legacy Bios machine, which is the only type of flash drive the Win 7 USB Tool will create... The selections would be different in RUFUS for a UEFI machine...