NullRef error while trying to animate a character

Now unity is really starting to piss me off here. I am trying to animate a character i got off the internet, but it's just BROKEN! now let me explain. I try to record movements, and half the time it doesnt capture them, instead, it just outputs NullReferenceExceptions about Failing to add a curve or something. Then also, when i try to move the character in position, it just teleports him somewhere else for the start of the animation. When i look there, he just stays there! No matter what i do, i cant get it to work. Now, i tried doing stuff like editing the rig of the character through Unity only though, i tried setting the rig to the other options too. The only one that seemed to sort of work was Legacy, but even that had the same exact issues. I dont have any idea what this madness is, but i just cant figure this one out! I tried it on the Standard Assets's Ethan and to no surprise, it worked flawlessly. https://imgur.com/a/kZcu96d

Update: Tried using some assets from the official Asset store, and its the exact same story. Why does nothing work suddenly?! Please help