I don't think the problem is Windows 10 itself, but the new browser named "Edge" that comes with it. Despite all the hoopla about how much faster, better, simpler, (and every other "-er" known to mankind) it's advertised to be, I am less than thrilled with it's functionality, plus I don't find it at all faster than IE, which is probably the low end of any speed standard!
I have discovered several quirks when trying to edit pages using Edge and I strongly suspect that this is another glitch in how it works.
Have you tried a different browser, Bill?