An amateur experiment with P/L 42.5 lens on GM1 & EP5

I'm getting some big differences between these two cameras (Olympus E-P5 and Panasonic GM1) with the P/L 42.5mm lens regarding "banding".

These are straight out of camera JPGs. I set shutter speed to 1/500 to minimize hand shake (overkill I know). The first is the lens on the GM1 which was set to 1/500, camera set aperture at f1.2. All SOOC JPGs, manual exposure, kept F1.2 aperture on all shots because I think it would show banding better. The only difference is used the EP5's 5 axis IBIS with 0 second anti-shock and with the GM1 used O.I.S. in lens and electronic shutter. All handheld because 99% of my shooting is handheld. I couldn't figure out how to get more variance in ISOs on the GM1, it might be in the menu somewhere but I've only had the GM1 about a month (since have upgraded to GM5) or so and I've had the EP5 over a year. This might explain why I get a bit more detail in the EP5 images because I've tweaked the camera settings.

GM1 at ISO 1600

GM1 at ISO 3200

GM1 at ISO 6400

GM1 at ISO 12800, I can see banding in the shadows.

GM1 at ISO 25600

EP5 at ISO 1000

EP5 at ISO 2000

EP5 at ISO 2500

EP5 at ISO 3200, I can see banding in the shadows.

EP5 at ISO 6400

This experiment was only to determine when and where banding would appear at higher ISOs. I am somewhat surprised that the diminutive GM1 does so well at such high ISOs. I need to tweak this camera a little to get more shadow detail in JPGs. I am also a little disappointed that the EP5 shows such banding beginning at ISO 3200. I hope any of you out there reading this long boring post might offer some insight into this problem. And I thought only the tiny Panny (legendary) 20mm f1.7 didn't play well with Olympus cameras. I am still extremely happy someone gave me this super expensive lens because if I'd paid for it myself I'd have more mixed feelings about my purchase. For now I will truly enjoy my fantastic gift and just remember to keep the ISOs lower on the EP5 with this lens. I created a 'Myset' on the EP5 just for this lens. The other lens I was gifted, the P/L 15mm f1.7 shows no banding on either camera at any ISO. Please remember that I am an amateur as was this experiment.

The only light was sunlight from an open window to the left of the camera.

Bobby