Set Slice (row, columns, measures) for a Flat Report to Yield Row Uniqueness

We have a flat report (rows + cols w/no hierarchy) that wasn't using any slices. Everything worked except for when we try to get the row heights to save. Our json only has ordinals for the rows - not column identifiers like your samples. We've tried adding slices (rows, cols, and measures), but we don't get anything but indexes for the row identifiers. 

The problem is that when the report re-renders, the row heights are applied, but seldom to the correct row - even tho the data is the same. So if i set the row height on row 2, the json may show rows > tuple > 1, and when the report is re-rendered, row 11 is the one with the row height applied.

We're using blazor wasm, so the samples and our code are very different and not that easy to create samples for sharing, so i hope the screenshots are enough to get the issue across.