[Scripting Question] Why does my custom ability change to Thick Fat

When I was doing some scripting to make a new ability to make use of Field Effects in Pokemon Rejuvenation, I came across an issue where when I loaded up the game any Pokemon that was supposed to have a custom ability would have it replaced by Thick Fat or Early Bird.
if isConst?(ability,PBAbilities,:DOOMDRIVE) && onactive &&
$fefieldeffect!=35 && $fefieldeffect!=35
$fetempfield = 35
$fefieldeffect = $fetempfield
@battle.pbChangeBGSprite
@battle.field.effects[PBEffects::Terrain]=7
@battle.field.effects[PBEffects::Terrain]=10 if isConst?(item,PBItems,:AMPLIFIELDROCK)
@battle.pbDisplay(_INTL("The beginning of a new era!"))
end

This is the Script i'm currently having issues with and it would be a huge help if someone could figure it out. Thanks a bunch for anyone who even offer a suggestion

So, starting with the simplest explanation just in case, have you added the ability to the appropriate PBS files (abilities and pokemon)?

Poq said:

So, starting with the simplest explanation just in case, have you added the ability to the appropriate PBS files (abilities and pokemon)?

Click to expand...

Yes, idk what the issue is but any pokemon with the ability "Doom Drive" will get either Thick Fat or Early Bird

Are those alternate abilities for those pok?mon? Or abilities from a prior version? Or is it completely random?

Poq said:

Are those alternate abilities for those pok?mon? Or abilities from a prior version? Or is it completely random?

Click to expand...

It seems completely random, the pokemon i'm attempting to put this on is a custom one that should never have had either of those abilities

I was afraid you'd say that...
Sorry, I'm stumped. :(

No problem, it's a pretty stumpy problem