How to correctly use the Collada exporter? I finally managed to finish creating a complete character in Blender and i wanted to export it for the Godot game engine, so i wanted to use Collada (i tried both the Blender default exporter and the better Collada exporter from the Godot website) as my exporting format but when i tried to export i stumbled upon some weird errors that i couldn't really find an answer on google. Here is an image with the errors i'm getting : 

I imported the .dae file into the Godot engine to see if it has any problems and the shirt of the character is invisible but only the front side and when i play the idle animation the hands deform weirdly.

I would appreciate if you guys could help me with this or tell me what i should search to fix and avoid these errors in the future.
Try applying scale, rotation and location(Ctrl + A) on the rig and then the mesh, while in Object Mode.

You'll have to redo the animation