This worked for me.
I received a new WinWing FPF7 for the PMDG 777, and after installing it I noticed that all button presses were being registered twice in the sim (but not in SimApp Pro for some reason). Of course, I had already installed the latest version of SimApp Pro.
After finding this forum, I tried the suggested solution to roll back to version 1.16.57 — and it worked like a charm. Once I downgraded SimApp Pro, everything functioned as expected.
Thanks!