Hands look fine in Blender/Unity config, but fingers get all twisted in game?

I’m learning modeling to make new avatars from scratch.
I’ve rigged the hand of a character I’m making and posed it in T-pose in Blender. When I import this model into Unity and go into the T-pose configuration, everything looks alright.

However, when I actually open up the game and test my avatar, the default rest position of the hand is all wrong. Mainly,

  • The middle finger is curled far in compared to the other fingers

  • The pinky finger is too long and extended out compared to the other fingers

  • The pinky finger is twisted out away from the other two. (I think this applied to the middle/pointer finger to a lesser extent.)

Here are some screenshots to show what’s going on.

I have tried tweaking the roll of the bones, using alt+R in Blender to set all bone rolls to 0, tweaking around the position of the finger bones, manually tweaking around the fingers in the T-pose configuration in Unity, and the bone names and vertex groups/weight paints are all correct. So far this finger-bending-twisting issue is blocking me from finishing this avatar and I’ve been tearing my hair out about it for a few days now!

If anyone in this community has seen a problem like this before or knows what could be going wrong or what’s leading to this that could be fixed, I’d definitely be blessed to hear it.

I know this is a bit of an unconventional hand rig since there are only two finger sections and four fingers instead of five, but I’ve seen other avatars with four fingers and the bones set up in a way similar to this that didn’t have these issues.