On a shoot the other day I was regularly unable to adjust aperture or focus on the Lumix 42.5 f1.7 lens coupled with the Panasonic GH4. Removing and reconnecting the lens and turning the camera on and off would ultimately work- but often it would take several tries to get it functioning again.

I have never had such problems with any of my other (Panasonic) lenses and this one is new. Is there something I can do/has anyone ever experienced this? Clean the connectors with some fluid?

I still have warranty and could send it in but I could lose the lens for 3-4 weeks and I most likely need it before that...

This looks like a lens malfunction, I would just send it back now, if you don't you might be able to use it the following weeks but it's of no use if i doesn't work at a shoot.

Thanks, Noa, just got word from tech repair that I can try cleaning the connectors with alcohol. I haven't even tried that yet but every time I switch on the camera, the lens now seems to work fine. I will clean the connectors and give it a shot and bring the 12-35 with me as backup.
The job I need the lens for is static portraits, so no run 'n gun and chances of missing the moment...

At the back of the contact unit there is ribbon, flex cable - sometimes poorly soldered.