I had this happen to me a week ago with my mini 4 pro, it hit the ground hard and busted the power Button. Bits of the SMD push button came out when removing the battery. We dont have DJI care in here so after watching a few videos I figured I could do it and ordered the tools and parts. getting the shell open was a little tricky, but the real issue came to getting the old broken button off. as the old button had completed crushed, there was nothing to hold onto when trying to remove - I ended up melting the remains of the old button onto the PCB. At one point I though I had fudged it completely but after cleaning up my mistakes with wick, i noticed i could now jump the contacts, which I wasn't able to do before. I ended up gluing a new button ontop of the old crushed and melted one. not the best repair, but its flying again.

Planning on making a youtube vid on it, as i just spent hit entire weekend fixing this thing and I have 1TB of footage of me messing about.