Boot Camp Assistant keeps on failing.

Hello there.

I sincerely hope to see some help.

I've been trying to make a partition of Windows 10 on my Macbook Air 2014, which runs High Sierra, via Boot Camp Assistant, but I keep on failing.

I updated to the latest OS version and also redownloaded the Windows ISO file just in case it could possibly be out-of-date by now.

The HD has the free space of around 80GB out of 251GB (I can enlarge it more if necessary), and my 32GB USB is formatted through Disk Utility.

What the Boot Camp Assistant shows is that it starts copying Windows files into my USB under the selected tasks, then it gets stuck at the point slightly before it goes half the way, and says "Your bootable USB drive could not be created. There is not enough space available on the disk(3rd pic)."

I don't even understand what that last 'disk' exactly refers to; is it HD or USB? Either way, as mentioned, I believe both my HD and USB are supposed to have sufficient space already.

Plus, when I opened the used USB after Assistant failed, it had some files inside. That means the process was at least actually taken, but there was some sort of an issue that restrained it, I guess (last pic).

I've visited several websites and watched videos for guide, but none of em seems to work.

I have no idea by now.

What could be the cause of this thing?