First of all, please do not try playing the animations via Humanoid:LoadAnimation() and AnimationController:LoadAnimation as it can lead to replication issues. That’s why both methods were deprecated years ago, as stated here:
I recommend you to refrain to using the Animator included in the characters Humanoid, it’s there for a reason.
And there might also be conflicts because now you have 2 Animators as you create a new one and put it in the exact same path of the already auto-generated one. Please try loading it on the pre generated animator and tell us what’s happening exactly.