Loan Refund Stuck in Limbo

Apologies in advance for this ramble but I am looking for advice as to how to proceed.

I paid approximately $55,000 towards loans serviced by Great Lakes between March 2020 and early 2023. During that time, at least 2-3 loans were "paid in full". In mid-2023 Great Lakes merged with Nelnet and my loans were transferred. Around that same time, I decided to pursue PSLF (as I have been working for a non profit since 2020 and I would qualify for these free payments). I had my loans transferred from Nelnet to MOHELA in July 2023 and requested a loan refund in early August 2023 (before the deadline).

After multiple calls to MOHELA, my local congressman's office, my state attorney general's office, and complaints submitted on studentaid.gov, I eventually get a refund for ~ $30,000 in April 2024 (8 months after my request). I was obviously happy to finally get a refund but it was ~ $25,000 short of what I was owed. I called MOHELA right away and inquired about the remaining refund and their response is that they did not have record of the remaining balance. During my correspondence with my state AG office, I was provided the phone number for the "director of business development and government relations" at MOHELA. I called his number, left a voice mail, and within days a MOHELA Ombudsman specialist was assigned my case.

Initially I was hopeful that the Ombudsman specialist could resolve this issue but unfortunately created an even bigger headache. What I was told is that, because these loans were "paid in full", the refund would have to come from the servicer they were paid to. In this case that would be Great Lakes who again, no longer exists, so it would have to come from Nelnet. I worked my way through the Nelnet phone tree to a Nelnet Ombudsman specialist. Nelnet told me that they cannot issue the refund because that would involve adding the loan balance back to my account which they cannot do because they're not my current loan servicer. I called back the MOHELA ombudsman who reiterated that their hands are tied. They simply told me to submit a complaint on studentaid.gov which I already submitted 2 months ago without response.

As the title suggests, I feel like I am stuck in limbo and am worried I'll never see this money ever again. It's obviously a significant sum and I want to do everything in my power to get the refund. I have spent hours working through the MOHELA and NELNET phone trees and already sent updates to my congressman and state AG office but I am afraid their hands are tied as well.

I would appreciate any advice about how to proceed. If anyone else has been in a similar situation- was this ever resolved? If so, is there anything I should be doing that I haven't already?