Will my chain of command be able to chapter me if I fail the ABCP after having been injured for the past 5 months?

The only paperwork error that would make a flag erroneous is if you actually did not do the thing you were flagged for. If you were actually over bf%, then the flag is valid, even if it is removed later by the commander. You will know this is true if you look at your ERB and the flag section says "KE". K means ht/wt flag, E is for the type of removal. E is not for erroneous removals.

If you are pending a med board, your command will not be able to chapter you for ABCP. Once the MEB is initiated you will undergo the whole process and the CG determines which separation you receive. CGs do not separate MEB for ABCP or APFT failures ever. Now if you were pending MEB and had a DUI or substance abuse issue, that's a different story. Also, it takes a while to separate someone for ABCP. There's a mountain of paperwork the command has to provide showing you were seen by a nutritionist, a doctor, and other stuff. It's even harder while you're injured. It's not a fast process and commanders aren't trying to lose a good worker with no incoming replacement just because they're fat.

Finally, you will most certainly not receive a medical retirement with your time in service due to an injury. You would most likely receive a medical separation with a small payout of a few thousand dollars and probably some small disability payment from the VA as well as free Tricare for life. Without knowing your injury I can't say for sure, but unless it was grievous, you will almost certainly not receive medical retirement with under two years in service.

There is a lot that depends on context and details.

First off, if you are seriously injured you need to work with your medical provider and start have the discussion on whether this is something you fix or if you need to go the med board route.

Second, you have to be within height and weight while in. Whether you are on profile, full duty or limited duty while pending a med board you have to be within height and weight. That rain cloud isn't going away. You need to figure out how to maintain your weight.

Third, you say the flag in September was erroneous but the fact you are asking about a chapter makes me think it wasn't erroneous.
And lastly, you can't look at a chapter and med board as if they are the same because they aren't even close. One is a fast track for getting someone out and the other is checking all the boxes so someone who was injured during service is appropriately compensated. If you are injured get a med board but you need to get your weight in check.

You say the chapter was erroneous due to a paperwork error. Was the paperwork error a miscalculation of your BF%? (rhetorical question)

Yes, I understand the technicalities, but if you were *really* over in September (which, BTW, is no "no big deal") and you are over again now, then yes, you should be chaptered.

Now, depending on the nature of the paperwork error in September, it is possible that if your Commander initiates a chapter, you *may* be able to successfully fight it. But you need to talk to JAG - and *only* JAG about it. They can give you the real-life yes or no depending on the specifics of your situation. All of us here on RP are merely armchair quarterbacking it.

The better option is to not fail. You say there is nothing you can do to change it but you control what you eat and how much of it. You control how much you work out. Even on profile, you can still exercise. If you are close, then figure out a way to lose that last 1/2" or 1". If you are not close, then this is a bigger problem than having been on profile.

Finally, regarding medboard, if the Army broke you so bad that you can no longer serve, then you deserve to be compensated for that. Even if they broke you on day 2 of Basic Training. Think of it like worker's comp in the civilian world. I was shot on the job delivering pizza. I was out of work for three months. You can be damned sure that my employer paid every cent of my hospital bill, my follow up appointments, AND paid me to sit at home and recover. They would *still* be paying me if I had not found another job. If the Army broke you, they need to either pay to fix you, or compensate you for the jobs you are no longer able to do in the civilian world.