DJI just released a video on how to downgrade your drone’s firmware with the DJI Go 4 app. In the video, they show the procedure for a DJI Mavic 2 Pro, but I assume this works for any recent DJI drone. You basically press and hold the menu icon (three horizontal lines in the top right corner) for five seconds and a special firmware menu appears. You can now select which previous firmware version you would like to downgrade to. Check it out.