EDIT: Now fixed. Brilliant, Thank You! Now rated 5 Stars. (I wanted to post a new review but for some reason I now can't find the link to do so. Where did it go?)

I really like this add-on as it mosty works perfectly. I also appreciate how quickly the developer updates it when things do go wrong.
One issue that I am noticing right now is that on YouTube the availability of a download is a bit hit and miss, I would say roughly only about 70% of videos I try are available. Just a few minutes ago I was able to download 1 video from a channel but a 2nd from the same poster was no-go.
I sometimes find going back to a video sometime later will work but mostly not.
Clearing cache/cookies, re-starting browser, etc. makes no difference.
Would hope to see this fixed or at least learn what the issue is.
Tx.