I've had a total of 6 samples of this lens on my A7, and most of them benefitted from Live View settings set to ON when photographing at f/8 as I usually do; my present copy's sharpness also improves by this measure, it's just not critically sharp at f/8 when Live View settings is set to OFF. It doesn't make a difference wide-open though and I don't know if your A7M2 behaves differently. It's worth a try, I'd say.The lens is definitely capable of some nice images, but doesn't impress me too much when pixel peeping... but maybe I'm just not used to zoom lenses. Idk, sometimes I like it, sometimes I don't. Maybe I just need to stop down more often.
Also, focus accuracy is helped by a large focus area. I get the most consistent results when using a large or medium size flexible spot or, when subject matter allows, the wide setting for the AF area. I agree, it's difficult to push this lens to optimal results, but when you succeed the image quality can be excellent provided you keep the focal length between roughly 35mm and 60mm. As universally documented, corner sharpness degrades below 35mm and 70mm is not all that strong either.