...
I cannot right-click while sitting at the "Enter seed (25 words):" prompt. Trying again, I also cannot paste using either method to the password prompt.
...
I don't have a Win 10 box to check this on, but a couple of suggestions:
1) When you right click the title bar of the command prompt window, do you have an "Edit" sub-menu? Win 7 does, and it has a "Paste" option.
2) Also in Win 7 you can left click the icon that looks like a C:\ DOS window (upper left corner of the command prompt window) and choose "Edit" -> "Paste".
Rather than dash off a snappy response about wasting more of my time, I decided instead to try your first suggestion and, low-n-behold, it worked...

So, not really sure what is going on here, but I can confirm that manually selecting paste from the right-click menu in the title bar does, indeed, paste text into both the password and recovery seed prompts in the wallet.
I suspect this only makes the proverbial water muddier, though, as far as finding a root cause/solution.
EDIT - I did not try #2, but you do get the same menu by left clicking on the DOS box icon.