I can help guide you in rolling it back.A friend took time to write this up and I have done this many times.. Read this guide completely and make sure you understand what we are doing. Let me know if there is something you are not sure of. If you need FW or files, let me know.
https://phantompilots.com/threads/downgrading-firmware-on-p3p-from-1-10-9-to-1-7-6.105384/
https://phantompilots.com/threads/downgrading-firmware-on-p3p-from-1-10-9-to-1-7-6.105384/