INDEX/MATCH - not working quite right

[awrex]

I have a index/match formula that returns the contents of a cell from the prior month, however it's only working about 80% of the time.

I have 21 rows with the formula referencing corresponding worksheets. About 11 of them reference 2 months prior vs 1 month prior.

=INDEX('WORKSHEET1'!C9:N9,MATCH(TEXT(MONTH(TODAY()),"mmm"),'WORKSHEET1'!C1:N1,0))

Aside from different worksheets the formula is the same across all.

The worksheets referenced are all the same as far as layout goes, so I'm at a loss for what is the cause.

 

[awrex]

Actually looks like it's just returning the first month. Going through analysis paralysis...