I don't know if this is a Geckolib issue, or Tiny Dragons, but when the player is near a Tiny Dragon Skeleton the client log spams:
[18:26:25] [Render thread/INFO]: [software.bernie.geckolib.core.animation.AnimationProcessor:buildAnimationQueue:49]: Unable to find animation: 0 for SkeletonTileEntity
Client log: https://gist.github.com/kezmodius/984cd2b41efc5efa5c0b94d97660612f
I have also reported this to Tiny Dragons.

Yeah this is an issue on their end