Would it be that you're using too much juice?
There isn't enough sugar in juice to overwhelm and kill the yeast so as long as you don't add too much sugar yourself (the rule of thumb is keep the total sugar to 1100g in a DJ) it shouldn't stop early and should ferment to dry .990 given enough time.
I wouldn't trust everything you watch on YouTube!
There is a lot of useful stuff on Youtube and a lot of crap.
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