Uploading photos and other images in Facebook private messages

After I so-called “upgraded” to Windows 10, I was unable to post pictures from my computer into Fb private messages. (No problem putting them in regular Fb posts.) The Facebook uploader kept making dots to show it was trying, but the picture never appeared. As a last resort, instead of clicking to try to post a picture (Add Photo), I clicked to post a file (Add Files). It worked. Now all I have to do to upload a picture into a private Fb message is to find the picture in my computer files (besides my Pictures file, I store lots of photos and other images in my Documents file), click it, and there it is in the private message.

I hate Windows 10.

Edited to add that according to what Google told me, the problem is definitely associated with Windows 10, and the only possible (but not sure-fire) remedy is to disable some of your automatic computer maintenance functions.