DJI Mini 3 Pro. I live in Manhattan, NYC; no places nearby where I could fly it outside legally. So I tested it in my apartment.

No issues on the first flight, besides the drone refusing to fly into a hall with a partially-opened door, I'm assuming maybe due to collision detection. Ran out of battery so saved it for another run.

Second flight, it crashed (not sure how, as it happened during a split second where I wasn't looking at either the drone or the controller, and it seemed to be at around the same location on my first flight where the drone refused to fly further).

Ran it for 2 more flights directly afterwards, and both times it was out of control; moved forward or up without me telling it to, didn't seem to respond to my controller commands, and when I attempted to force it to land, it just kept bumping into the ceiling until it eventually fell (flight #3) or ran into a wall (flight #4).

All 8 propellers are visibly scraped or damaged, a few with tiny parts scraped off. I presume some of this damage may have at least partly contributed to the lack of control on flights #3-4. The product only came with 4 spare propellers, so I guess I'd have to buy 4 more.

After replacing the propellers, for the next run I'd definitely fly it outdoors, in an area where I'm legally allowed to do so (may require a little travel). However I'm slightly concerned the drone will be out of control again and just keep flying up or away like it did on flights #3-4 (and perhaps even started doing to a degree on flight #2). And, if this loss of control happens outside, then it could just disappear, and/or suffer a fatal crash.

Does anyone have any theories on why the drone flew fine on run #1, but started going haywire on subsequent runs? And is there anything anyone would advise I check for to ensure it flies correctly on the next runs, besides replacing the propellers? I didn't opt for DJI Care Refresh within the first 48 hours, because I didn't think it would have technical issues and become damaged so soon. Thanks in advance.

Avoid flying indoors.
Take your drone out to a nice open area, away from trees and buildings and it will fly just fine,

Or perhaps buy a smaller indoor drone to enjoy yourself at home...

"Does anyone have any theories on why the drone flew fine on run #1, but started going haywire on subsequent runs"

Are you aware of sports mode vs cine mode?
Are you aware of APAS mode which wont make it crash in flying indoors?

Flying indoor needs skilled pilot without GPS available, if you are beginner (I am not sure) then use propeller guards & use APAS switched ON for flying in NORMAL mode or after take off switch & fly in CINE mode.

The reason it crashed are possibly can be any one of these.
You thought you were flying in CINE mode as the switch was set to cine mode but if you land & take off again by default it switched to NORMAL mode even though you were seeing it set to Cine mode.

You accidentally switched to sports mode & may not have skills to handle the throttle in sports mode (Indoor with sports need all together different level of skill set)

Hope this helps.

Hi, cmhawke. Thank you for reaching out. We are sincerely sorry to read about what happened. Please refer to some recommendations of other users above. And since the drone crashed, we highly recommend that you send your drone back to us for further diagnosis. You may submit an online repair request through this link: {https://repair.dji.com/repair/index}. If you need assistance creating a ticket, contact DJI support at (https://www.dji.com/support). Your kind understanding is appreciated and thank you for your continued support.