Bread and Butter Workhorse Lens: Pan 12-35 f/2.8

My experience is much the same as yours, using the 12-35 on the GX7 and the G6. An all round lens of considerable quality which is my main lens these days. I have had no problems with SS with this lens on either my GX7 or G6.

I don't believe the Oly 12-40 is sharper and certainly it could not be better built -- the build quality of the 12-35 is exceptional.

Flare

I don't think you mentioned flare. I find the lens is subject to flare of the general nature of light across the frame over a pretty narrow angle when the light is just outside the frame. A small adjustment of viewpoint eliminates it.

I also came across it when I was photographing singers at a concert -- lights behind them could show up as double images around the center point of the frame. Again, once aware of this you can avoid it by a small change of viewpoint or if not avoid it, turn it into a positive by positioning to take advantage of the flare as a picture element. I first noticed it when I gave a rotund rock singer a large green navel! LOL.

Lens hood

It is incredible, isn't it, that Panny could make a beautifully engineered lens and add a lens hood that doesn't stay on properly! The hoods I have on the 45-150 and 100-300 are fine -- they stanp int oplace and stay in place and those are cheap lenses (comparatively).

It appears the teeth on the lens hood track and the sockets on the lens bayonet are not matched. Someone on this forum suggested some surgery involving cutting a new socket and enlarging the teeth with epoxy resin. That’s a bit beyond my level of finesse. Someone else suggested tape -- I now have a thin strip of plastic electrical tape right around the the lens bayonet. It takes a little bit of force get the hood over it and then twist it into position, and once in place, it is pretty much a permanent installation. The only time that troubles me is on the odd occasion when I want to use the pop-up flash with the lens, in which case you get a big shadow in the bottom of the frame which is much reduced when the hood is removed.

But at least I am now assured of it staying in position and not spoiling photos by slipping around, and not spoiling my day by being falling off and being lost altogether!