Just had a quick look and, indeed, you're absolutely correct, thanks a lot for the hint! The array function counting the OHKs seem to work... sometimes, but not consistently for whatever reason. I've switched it out against a non-array version that seems to have no issues.
However, I couldn't reproduce the counting error for natural hits in any way. Do you consistently get this or only once in a while?
I think I used the sheet only twice (Excel starts) by now without PC restart, but it did not work on any of these occasions.
I will retry tomorrow and write you. Or maybe someone else can post in the meantime.