@mies43 Instead of a private window try using a Guest Profile window (Menu --> More tools --> Guest profile) and make sure you close your original profile window before testing.
This seems like an extensions issue to me. I know that you said you tested without them, but did you actually disable the extensions when testing? If not, can you please try doing so and testing again in your main profile?
If that does not work, would it be possible for you to share a short screen recording of the behavior as seen on your end?