My manager edited my time cards to remove OT and HR doesn’t seem to be doing a proper investigation into it.

Location: Oregon

I found out that my manager had been editing down my time cards. It probably started early 2024 when I started reporting to them. I don’t think it was a LOT of overtime that they erased, but the time frame is large. So, I don’t know. HR has been investigating/auditing for almost a month now. Apparently they can see my original punches and the overrides and are recalculating to my understanding. Yesterday, they came back to say that they owe me $300ish for 2025. That sounded like the amount I was expecting for the time card that I had flagged to them (the one that prompted me to go back and look at other ones). I asked the HR to share those records/analysis with me and asked how far back they reviewed. HR responded saying that I’m now owed 5 hours of OT for 2025, but didn’t share why. I feel like I’m expecting 2-3 hours the week I flagged and I’m not sure if 2-3 hours covers the rest of the year. I asked for records again, because there’s 50ish suspicious dates that I would like to verify were counted. I feel like HR is going to be cagey sharing those with me and my hours worked are going to be a weird negotiation based on the last two emails. I’m over the income limit for BOLI. Apparently they’re overwhelmed right now. Any advice on this and how to best handle?

Edit: Wanted to add that this is a pretty big company (300-500 employees).