Leaves dropping

So I got this tree from someone in the neighborhood giving it away at the end of Fall. Unbeknownst to me, when posted on Reddit, another user pointed out that it has a root girdling issue. Still, I'm excited to see it fill out and watch it grow while its still alive 😆. I noticed it was starting to get some buds opening, but also noticed quite a few had dropped off. I'm not sure if this is a water/nutrient/ environment issue, or if maybe squirrels are getting to it for some reason. I've done nothing other than water it once or twice since I've had it. Any advice is appreciated.