Have you noticed that when you press alt gr + space in terminal window, a non-breakable space character is outputted? It looks just like normal space but it prevents commands from working.
From example ’[alt gr + space] ls’ cannot be interpreted but ’[space] ls’.
Solution is to change keyboard behaviour:
This feature can be configured in:
->Using space key to input non-breakable…
Change the setting to ’usual space at any level’ setting.
Please note that this problem may not occur in some keyboard layouts.