I spotted something that might be of interest there's a split second when the error occurs that the URL contains an error message. A human could never read this message in real time, but you can capture a screenshot of a video of the error. (Of course I only know about this because I am having the same issue...)
The error message appears to complain about "User+Is+Invalid" and "username%40zendesk.minecraft.net+has+already+been+taken" (username would be the name of the account.)
Update, I found another fix however this fix does not work on easy mode and has a 50% failure chance on normal. Aka zombifying the affected villager fixes the bug, however this solution is unviable on any difficulty other than hard.
I've been having a similar issue with my space suit, my helmet has a transparent dark overlay, but is isn't showing up when the skin is active in the preview. Active referring to when it is the currently equipped skin or when using the edit skin button. Somewhat amusingly it shows up properly in the display that shows all of the skins in your wardrobe. so this visual bug only affects the animated preview.
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Could this "bug" be kindly unfixed? Sprint Sneaking is one of the best mechanics in the game and makes raiding Ancient Cities actually fun. Slowly sneaking around isn't fun, but stealthily dashing about with the Sprint Sneak while dodging sensors is a lot of fun. I literally get Swift Sneak specifically for use with Sprint Sneaking.
Also who honestly wants to reinput the sprint button every time they eat, I'm calling it now, people who never knew this was a "bug" are going to complain when they find out that eating now cancels their sprint.
My take is, if fixing a "bug" makes the game feel more sluggish and less fun, that is not a "bug" that you want to fix.