Joakim - thanks for digging up those examples. It's exactly the same as what I got with the Canon 1D back then. I wonder if the strange effect with the M240 and 35/1.7 flare is sensor or lens related...
I recall shooting some sun-in-frame images with the ZM21/2.8... I'd have to go back to the out takes from that day to see if I also got the tearing. I think I did, but found that if I stopped down enough, it didn't happen... like probably to f/16. It's probably related to how intense the light is, thus overloading the circuitry.