A7s II focus hunting issue

[Beka]

Hello there, sony shooters! It is my first post here. I searched a lot but I couldn't find any solution related to my problem. So it goes like this:

I have Sony A7s II and I had attached 50mm f/1.8 lens on it. When I was switching my camera to continuous autofocus, it was starting to hunt for a focus, never mind it was night or day, it was at 1.8 or 9, it was hunting for a focus hopelessly. Then I bought Tamron 28-75mm f/2.8 and again, it started hunting for a focus. This happens if camera is standby and I press shutter button for focus during photo. But if I switch it on video mode, everything is perfect and everything works very well. Even when I shoot video AF is great, Eye-AF also works perfectly, but when I want to shoot, say, my running dog, every image is out of focus.

Did any of you have such an issue? What's a problem? I tried every focus mode but problem continues. 

Edited: I almost missed that it Tamron and Sony 50mm lens worked perfectly on a73.

Thanks for your attention and sorry, if such post existed before. If so, please link me

Happy shooting!

Edited February 4, 2019 by Beka