When me or my friends wear a Platinum Chestplate (wyrmroost:platinum_chestplate) the game crashes. I use Forge 1.16.3 34.1.43.

You need to provide more info, developers cannot magically know what's causing the crash without a crash report or log file. Please send one so your issue can be looked into properly.

I think this is the crash log of platinum chestplate: crash-2021-01-27_18.54.39-client.txt

You have a corrupted jar file, please redownload on curseforge