It happened to me once. First at all, before doing anything else, print a new diagnostic image on a glossy or satin paper. Check that ONLY the MK-R is having banding. If all the other printhead are having banding, you probably have an "advance paper calibration" issue (it can be solved easily, or not).
Do an advanced calibration test with the same paper (it is important that the paper loaded coincides with the paper preset), check the results and see what happens. Do not clean the printheads by menu or by hand before checking out the results. If after the Advanced Calibration test you still have banding, you must do a "service calibration procedure" that it`s the service manual.
I hope this helps.