The preset no. will continue to flash if no preset has been stored in this preset number (ie the preset slot is empty). This is because the M300 / M350 comes without any presets stored in the preset slots (See also this FAQ: Where are the factory presets
). Try to store the current setting by pressing Store for a few seconds. Press Arrow up to the next preset, press STORE for a few seconds (to store another preset), press arrow down (the previous preset number flashes), press LOAD and it will stop flashing.