Dying sheeps doesn't always work

Sometimes (around one third of the times) once I dye sheep it seems to work for a while but then I get the dye back, when I shear the sheep I get the correct color of wool but once it goes back it's of the original color (the sheep were mostly white and only white sheep seemed to be affected, would need some more testing to confirm).
Update: if a click on an already colored bugged sheep I'm able to use the dye once again