It has been my experience that using V2 of DJI Assistant is the most reliable way to update firmware. I didn't even try it yesterday with Go4 and with DJIA, the aircraft update went smoothly although it did take a bit longer than ten minutes. However, I temporarily forgot about updating the RC and when I connected via Go4, I didn't get notification that it needed an update. But, when I remembered and connected the RC to DJIA, it did indicate that an update was available and that went smoothly as well plus, a good bit quicker than the aircraft update.
Haven't been out to fly since either update but hopefully, today.
KB
Edit: Got out the next day and flew without issue using an iPad 9.7.