Can your 45 days of extra duty be reset if you’re late one time?

I don't think they can do that. Unless they give you another Article 15 (for being late), I don't see how they have the legal standing to "reset" your extra duty. That essentially gives you 77 days of extra duty for the initial offense, which is beyond the scope of a field grade article 15. Plus, that could be viewed as "double punishment", where a punishment (even a portion of it) may not again be imposed for the same offense under Article 15. I'd consult with Legal for an official opinion on that.

The tribe says see JAG. Make sure you are focusing on the right thing. Absent a regulation, policy, process, or whatever, an administrative event can be punished and repunished. It's a morale killer and a trash leadership action. If there isn't the aforementioned basis, IG can't help because you can't claim improper action if there's nothing to bounce it against. People forget that Constitutional protections don't apply to administrative actions. That's why "Taking the Fifth" is grounds for termination. It's been a while, but I recall many of the accused protections had to be incorporated into the regulations precisely because military law is a different animal. Bottom line, you are looking for written guidance from a governing authority, NOT local Barney Fife opinion. If JAG opinion only, standby for something that you might not like as JAG is there to service the Command, not individual SMs. One thing having a lender out in town trying to beat you up. Another thing when it's between you and the Brass.

The Army used to have Correctional Custody Camps which was also called School of the Soldier. The 197th Inf Bde at Fort Benning had one on Kelley Hill. Soldier cound be sent there by their commander with or without ART15s. It was desighned to motivate Soldiers and keep them out of the stockade or UCMJ. I had to escort many Soldiers from both the stockage and CCC to the hospital and other admin places on post. You were always armed when escorting a prisoner. CCC Soldiers, no arms. Every Soldier I had that been through Correctional Custody were highly motivate after they went back to the platoon.