Steam emoticon displays as a red error box

For a while now I've noticed that a specific Steam emote (:csgohelmet:
) displays as what looks like an "error" image, both in the emote picker and the chat itself. However the higher resolution preview image (when you hover over the emote) displays correctly.
I've had a look around and it appears this is a relatively common problem, however I haven't been able to find a solution anywhere.
The only suggested fix I've found is to restart you PC, however since this has been broken for months and my PC has been restarted countless times, this doesn't appear to be a good fix.
Is there any known way to fix this?
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How do I unlock steam emoticons?
You have to collect a full set of trading cards for the game, either through purchases made in the Community market trading with friends. Once you have a full set, you can craft the badge. You can also trade emotes with friends.Image to Steam Emoticon | COMPLETE GUIDE
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