What type of reusable filter do you have? I use "perfect pods" (https://smile.amazon.com/Perfect-Pod-ECO-Save-Refillable-Integrated/dp/B07SJB168V/) and while I sometimes get some grounds it is nothing horrible. I have also used the "My K-cup" (where you replace the k-cup holder) and found there was a trick or two to get a better brew, but never had issues with grounds.