Typing the / key opens the chat screen, which seems to be intended as a shortcut for typing commands. However, the chat line opens with two slashes ("//") in front, meaning that the first thing you need to do after opening the chat screen in this way is to press backspace, to delete the superfluous slash.
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Asteraoth
Thank you for your report!
However, this issue is a Duplicate of MC-122477.
If you have additional information, please add it to that report.
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