Sweet..so they must have fixed it! Thats good news. Mine was two different batches of both reagents so I knew it wasn't a bad batch. This was around December '22.I got virtually identical test results using both HI772 and HI755. I tested each 3 times. HI772 results: 8.3, 8.4, 8.3 and HI755 results: 8.3, 8.3, 8.3. Hence, no issue with interchangeability at least with the reagent batch I received.