I'm using a formula to compare two cells to an "index table" to determine a
value as follows:

=INDEX(Grid!$B$2:$CL$90,MATCH(D16,Grid!$B$2:$CL$2, 1),MATCH(D17,Grid!$B$2:$B$90,1))

My issue is that sometimes the formula works and gives me the correct value,
but sometimes it looks up "D17" on B2:CL2 and "D16" on B2:B90 -- basically
it's reversing where the match matches. Does anyone know why it does this?
I'm not finding a "method to the madness"; it's just sporadic.