Error message upon opening and macro buttons are gone

I have a workbook with a bunch of small macros in it that's doing some weird things and am wondering if anyone here may know why. Long story short, I've been trying to identify a bug in one of the macros that causes the macro to select the wrong cells the first time I run it. Haven't figured that one out yet, but what's weird is the macro works fine every time after the first time running it. I'm sure it has something in common with the issue I'm about to explain.

I just saved, closed, and re-opened the workbook several times to try to replicate the error, and then suddenly upon opening the file again, I received this message: "Excel found unreadable content in 'filename' Do you want to recover the contents of this workbook? If you trust the source of this workbook, click Yes." And when I click Yes, the file opens, but says "Repaired" up top. When I click Enable Editing, a dialog box opens titled "Repairs to 'filename'" and has this in it:

"Excel completed file level validation and repair. Some parts of this workbook may have been repaired or discarded.
Repaired Part: /xl/worksheets/sheet1.xml part with XML error. Load error. Line 2, column 0."

Now my buttons are gone on the sheet I was trying to find the bug in. What I don't understand is I didn't change any code in the macros associated with this sheet, all I've been doing is opening, saving closing, and re-opening to try to replicate the issue. Has anyone ever seen this before or know what may have caused this to happen?