MacBook Pro (Retina, 15-inch, Mid 2015), running macOS Catalina 10.15.5.
Sometimes while working, the built-in keyboard becomes completely unresponsive, the only button that works is the power button. Logging-off, sleeping etc. does nothing, only shut down and fresh boot (with the chime) removes the issue.
While the issue is happening, the Caps Lock light is turned on.
Touchpad works fine, and plugging external USB keyboard also works (but doesn't unlock the built-in keyboard).
Mouse Keys, all this stuff is turned off.
I noticed, but have no proof, that this happens when I'm pressing various left-side modifier keys: shift, alt, ctrl, cmd, tab.
Is this a hardware issue? A software issue? A hidden shortcut? Is there some kind of logging that can be turned on to watch for this kind of things?