Hyperactive screen after replacement.

I recently replaced the digitiser and screen on iPhone 5. All working perfectly for the first week or so and then the phone started to activate apps, make calls, surf web and generally misbehave without human interaction. Makes using phone almost impossible due to these symptoms occurring whilst trying to use phone as well. Key pad activates making typing impossible. To stop it I need to lock then unlock phone and this gives a temporary reprieve.

I have checked all cable connections and everything internal appears ok.

Could this be a static electricity build up issue?

I need help!