Curious problem with ioscbank

Hey,

I have encountered a strange problem with the attached patch.
Basically it's an [ioscbank~] that stacks fifths.

If I have debug watchpoints after the two [swap] outlets and the "clear" message, everything works fine.
The fiths get stacked and I get the expected harmonic content.
But... as soon as I remove the watchpoints, I only have one frequency at a time. I am unable to debug the problem, because debugging alters the outcome.

Thank you for your help!