1airlee, please check if you also has this symptom: Back soft button or Bing search soft button triggers when you light press around the upper left edge of the screen. If you lay down your phone on a flat surface and do this light pressing, are you able to feel or see a slight movement? You should not see this around any of the other three edges. They are stiff. If you have this symptom I think my fix can also work for you. Let me know.
Also, do you utilize any cover for your phone and did you notice if the issues started after using the cover or after a drop/shock of the phone?