Rinse-and-run is not enough. Sugar residue in the dispensing path is mold food, and the spout gasket is where group members keep finding black buildup. After each use, run a warm rinse cycle, then break down the vessel, paddle, and spout, and wash them. Pull the dispensing gasket out and scrub it separately; that is the part everyone misses.
Empty the vessel, run a rinse cycle with warm water to flush the internals, then wash the vessel, auger, lid, and spout parts in warm soapy water. Do not let a sugary batch sit in the machine overnight.
The dispensing spout has a removable rubber gasket, and mold grows behind it invisibly. Pop it out on cleaning day, scrub it, and let it dry fully before reassembly. If it already shows black spots that do not scrub out, replace it rather than bleaching it to death.
Weekly with regular use: full teardown of every removable part, plus a wipe of the condenser vents. Milk- or cream-based batches (frosty copycats, coffee frappes) should get the full teardown the same day, every time.
Check your model's manual for which parts are top-rack safe. Hand-washing the gaskets and seals extends their life either way.
No. Remove the gasket and spout parts, scrub them, and sanitize. Replace the gasket if spots remain. Then make gasket removal part of the routine; it grows back where cleaning skips.