Variation to my last IF OR formula

Hi again
I thought I would be able to modify the last formula that I got from the good people on here to another similar spreadsheet that I have. It is a simple case of adding another criteria to the list. I've attached the simplified spreadsheet showing what I want to achieve. The previous formula I was given was:

=IF(OR(A2="NIS",C2="NIS"),"X",IF(OR(A2={"PPA",0}),IF(OR(C2={"PPA",0}),"BOTH","BEFORE"),IF(OR(C2={"PPA",0}),"AFTER","")))

Which has worked perfectly before the additional test of AVONWOOD being added into the equation. I have tried:

=
IF(OR(A2="NIS",C2="NIS"),"X",
IF(OR(A2="AVONWOOD",C2="AVONWOOD"),"X",
IF(OR(A2={"PPA",0}),
IF(OR(C2={"PPA",0}),"BOTH","BEFORE"),
IF(OR(C2={"PPA",0}),"AFTER",""))))

which follows the same pattern as the previous formula but I'm getting wrong answers.

Can anyone help please?