Well, it was so hard to identify the cause of the issue and I think I managed to solve it.
It happens when the app tries to access remote objects on a key event.
It is so strange because accessing remote objects must not be anything to do with CapsLock, so it is surely an Electron or chromium’s bug 
I implemented a workaround for this issue in v5.6.3-beta.0.
@Alessandro_Baldoni Can you please try it?
@anon82854204 Yeah that sounds strange but I don’t have such an issue in my environment except for the CapsLock one. Please let me know if the issue persists in v5.6.3-beta.0!