Emojis not showing correctly?

[C6ckneyGeezer]

Hi guys! Hopefully somebody can give me a bit of help with a small issue I seem to have developed.

For months I have has emojis in my nav and node titles. It gave a splash of colour to things, it looks great imo.

However as of yesterday some of the emojis now don't show correctly. Why is this? See below. Any help much appreciated!