External Projector Not Recognized After Display Mode Change

On my MacBook Pro (M4), after connecting a Ricoh projector and changing the display mode (somewhat unintentionally, e.g., mirror/extend), the projector stopped receiving any signal.

System Preferences still and always shows only one display, although the MacBook screen somehow reshaped a bit when plugging the projector cable.

The projector screen became black after a bit of flashing, seemingly indicating that it is connected to the MacBook.

Many times of switching ports and restarting the computer and the projector did not help.

Switching to other projectors works fine.

Another MacBook with exactly the same hardware works fine with this projector in question.

Finally I solved the problem myself (with the help of ChatGPT):

1. Disconnect the external projector.

2. Delete the display cache files (/Library/Preferences/com.apple.windowserver.plist and ~/Library/Preferences/ByHost/com.apple.windowserver.*). This is suggested by ChatGPT.

3. Restart the MacBook, then reconnect the projector.

I believe this is a bug of the macOS.

It somehow recognizes the external projector, but did not treat it as an external one.

Maybe (just my guess) it is treating and configuring it as an internal display, which of course would not work.