When a command block is opened, attempts to type in the command input field sometimes fail even when the field is focused and has a cursor in it. The field remains unusable until the dialog is closed and re-opened.
Steps to reproduce
Place a command block.
Interact with the command block to open the dialog.
Click the command input field. A green cursor appears as expected.
Start typing.
Expected behaviour
The text you typed is inserted at the green cursor.
Actual outcome
Sometimes, text does not get inserted at all when you type, despite there being a green cursor indicating that you can type.
Unfocusing and re-focusing the input does not fix the bug.
Closing and opening the command block dialog sometimes fixes the bug.
Confirmed!