Stuck with effect AC bonus (0)

Hi everyone!
I'm working on a new mod (my very first one actually) and have run into an issue I can't fix. Any advice would be much appreciated!

Here is what I've done:

I've created a copy of the original spcl643.spl (Werewolf form) and named it lvl6463.spl. I've added a global effect (Type: AC bonus (0)) so whenever my shapeshifter druid changes into a Werewolf, he gets the AC bonus I specified in the effect. This works just fine but the issue is, when he changes back to the natural human form, the global effect does not wear off somehow and his AC is set to 0 instead of the expected 9.

His base AC in human form is 9 (gets -1 dexterity bonus). When he changes to Werewolf form, his base AC is set to 1 by the effect I created and he also gets -2 dexterity bonus in this form which brings his AC to -1. However, when I change back to the natural human form, his AC becomes 0. This clearly shows that the global effect is still active and his AC is still set to 1 (still getting -1 dexterity bonus).

The timing mode on the effect is set to 'Instant/while equipped - 2' so when the modified werewolf form (lvl6436.spl) isn't active anymore, I would expect the AC effect to wear off. What am I doing wrong here?

I've tried to remove the above mentioned effect upon returning to human form by adding Remove effects by opcode (337) to the spell that activates human form (SPIN124.spl) but that didn't work.

Any suggestions?