Japanese input is sometimes not loaded

Hi Community!

There are some issue on starting Japanese input. I have no idea on what's the trigger is, but my Japanese input could not be loaded and the computer does not accept some input from the keyboard - for example, command+w, command+t, and Japanese input. Curiously, command+q works.

When it happens, my keyboard source says "........." on Japanese - Romaji area as an attached image. Usually, there should be some settings - like Live Conversion, Help, etc.

It could be solved only by restarting my computer, but I would like to know the exact issue and remove it, or would like to restart the process. Does any of you have any idea what I can do?

Thanks!