Terminated Installment Agreement With No Notice Or Warning

I had an ~$800k balance for the tax year of 2021, and was able to get on a payment plan through an installment agreement in May 2023. Since May 2023, I have paid $11k on the 28th of every month through an EFT transaction which automatically deducts it from my bank account and have not missed a single payment. I have also filed my annual taxes since then in a timely fashion, and am not delinquent in any manner (confirmed by an IRS agent through phone call yesterday).

I noticed on 28DEC2024 (Saturday, so I gave it until 02JAN2025, yesterday, with the holidays) that the payment hadn't been deducted from my account yet. I called the Collections department yesterday to see what was up, and after 2 hours of transfers and holds the agent told me my payment plan had been terminated, and she had no idea why. I asked if any notices had been sent out, and she saw nothing on my account. She escalated it to her manager and promised me a callback (not holding my breath).

I called twice again today and none of the agents I spoke with could provide me a reason why my payment plan was terminated. Was wondering if anyone else had similar experiences and could let me know what my next step would be?

According to https://www.irs.gov/irm/part5/irm_05-014-011 the IRS can only terminate agreements IF:

The Internal Revenue Service may propose termination of (place in default) installment agreements if taxpayers:

1. fail to pay an installment payment when due under the terms of an agreement;
2. fail to pay another tax liability at the time such liability is due; This includes related TINs for the same taxpayer. Examples would be a sole proprietor and an IMF or a partnership and an IMF. Affordable Care Act individual shared responsibility payment liabilities do not default an existing installment agreement.Note: Note:
3. fail to provide an updated financial statement upon request;
4. provided information prior to the date such agreement was entered into that was inaccurate or incomplete; or,
5. fail to pay a modified payment amount based upon updated financial information. (See IRM 5.14.4.1.1 Installment Agreements Financial Reviews, Below Deferral Level Accounts, Joint and Several Liability Relief Under Section 6015, Withdrawals and Multiple Entities).
6. It then explicitly states that "installment agreements may not be defaulted nor terminated for reasons other than those listed in this section."