Dyed sheeps drops white wool and regrows white after eating grass

Dyed sheeps drops, when shearing, white wool and wool regrows white after eating. This affects all colors except light gray and gray.

Just thought - my light gray and gray sheep were "natural colored" - so I didn't dye them. All the dyed sheep are affected, as I shear them, the sheared wool drop white and the sheep's wool regrow white after eating grass.

Update 3: After multiple attempt to redye the sheep's, I eventually got to get it right. But still strange, that I had to dye a sheep at least twice or more to stay the wool white after shearing.