Hello, Quinn! I finally managed to solve this puzzle, all thanks to you. All I did is that I found 2 certificates (Apple Root CA - G2 and Apple Root CA - G3) with overridden defaults for trust settings.
I think sometime in the past I changed the trust setting for those 2 certificates to "Always Trust" for some reason I can't even remember. All I did is change those settings back to Use System Defaults. Now stapling works all the time.
Thank you again from the bottom of my heart for guiding me through this maze!
Topic:
Code Signing
SubTopic:
Notarization