Question Animation plays okay in preview windows but at runtime it makes character strange look!

Hey , Currently I have 2 animations 1-Equip 2-Hold Gun. My brother made these in blender and I had imported them to unity to test the result. animation transition is very good in preview but at runtime its not!
it play very wired look animation kind of its like made up animation!

this is preview animation

and this is runtime result

what am I missing?
appreciate any help
thanks