Incorrect Deferral % - Overage

I'm not seeing an EPCRS solution to a situation where a participant had a 12% deferral rate, subsequently lowered it to 1% but the employer continued to defer 12% from the participants paycheck. Is this a situation where the excess over what was desired to be deferred can be returned to the participant or is the excess deferral over and above 1% stuck in trust?

Operational qualification failure of not following plan document. The correction is to return the excess amount. There are details regarding timing (e.g., EPCRS vs. VCP) and also reporting.