I use the "Paste plain" macro regularly and there are frequent occasions where the text is not pasted as plain but rather in a random font that is not present in the origin document or the destination document. I think it happens with apps like Word or OneNote but I'm not sure in what situation it happens, it seems random.
Apps like Word have a private clipboard, so you have to force the Word clipboard and system clipboards to sync.
There should be an API for doing this, but as far as I know there isn't one.
So – the only thing you can do is pop out of Word for a second and then pop back in.
You can run something like this in an Execute an AppleScript action:
tell application "SystemUIServer" activate end tell delay 0.1 tell application "Microsoft Word" activate end tell
Change the delay as necessary.
Thanks, I will try this.