Payments still default to paid-off payment plan

[mowgli]

I'm sorry if this has been addressed before, but I cannot seem to search for a complete phrase like "payment plan" in the search engine of this forum. If an account has a payment plan that has already been paid off, the checkbox "attached to payment plan" is checked by default whenever a payment is made; and if applied, the payment plan balance goes from zero to a credit. Does anyone know a way to stop this behavior? Thanx

[jordansparks]

What version? I put it down as a bug for now, but need to know the version.

[mowgli]

Usually I want to be sure to include the version; forgot this time. It was 6.6.26.