Dyed sheep reverting back to original colour

Upon reentering/loading my world, the sheep I had dyed the previous day don't 'hold' the dye and revert back to their original wool colour.

This has happened four days in a row now. The first time they reverted, three sheep did keep the dyed colours (see the red, orange and yellow) but the others didn't. Second, third and fourth day, same thing happened. I dyed the sheep each day with all the different colours and they kept changing back every time I logged back in.

After dying each time, I made sure to stay playing in that area for at least half an hour just in case but still no luck 😞

Not a huge deal/bug but just getting a tad tedious re-dying sheep over and over! 🙂