OC I created a program in Rust to fix the missing Defense IV after upgrading to Pixelmon on 1.16
You can find the downloads here (codeberg). This is a first basic working-state release that can only be controlled through the command line. I tested it working on both Windows and Linux. Unfortunately, you also need to have a back up of your save files before they were upgraded and broke when switching to Pixelmon 9.0+ (1.16)....