Employer Underpaid me for 8yrs d/t Clerical Error, and Refused to Pay Unpaid Wages

I originally posted in Finance but looks like it belongs here.

Recently, a series of events led me to question my employment records and discovered my total experience years were wrong. Wrong enough to put me in a completely different pay bracket for the last 8 years. HR admitted this error and my pay rate moving forward was fixed.

My job publishes the salary structure and experience based pay brackets, so I’m able to roughly calculate around 30k of wages owed in the last 3 yrs. To clarify HR never disclosed how pay brackets were determined until the pay rate correction. Every past communication where I’ve asked for clarity or explanation on how that was determined, I was basically told it’s not my prerogative to know.

I asked about backpay for lost wages which was a direct result of their clerical error, and they promptly refused, citing standards. No formal policy exists supporting this decision.

I’d requested HR to investigate my pay and employee record several times over the last 8 years. Every time my role underwent a salary adjustment to offset compression (3 times), I felt the adjustment was off and would ask them to verify the accuracy of my pay. At the conclusion of each investigation, I was told everything was correct as expected. They reminded me that they have a team of highly trained experts. Aka stay in your lane. Each request went to different HR/Admin leaders because we would get new people every couple years.

My employer has a strong legal team, and they’re infamous for wiggling out of accountability. I’m worried there are loopholes I’m unaware of, which could prevent them from honoring their pay structure. I’m scared to involve legal because I’m worried I could lose my job from recourse. Does anyone have experience with this? It sounds like they are honoring my request for a second look, but if this is another dead end what are the next steps?

** TO CLARIFY: I really enjoy my job, and I like where I work. It’s just unfortunate that our HR dropped the ball. I have a very supportive team, and I’m happy that I’m getting paid a fair wage now. I just want them to be held accountable and make things right.