The first two picture pairs show the inadvertent use of spot metering. I set the AEL button up for spot, and memo/toggle, and the AEL/Fn buttons positions to be swapped. When the Fn button was accidentally pressed unbeknownst to me just from handling the camera, overexposure occurred in the second pic from the spot reading the very dark window in the centre and lightening it to middle grey. A similar thing occurred in the second picture pair.
I found it all too easy to do this and have since switched these two buttons' functions back to their original locations. But I still keep the AEL set to spot.