I've been wearing my DW-5600e as a recreational beat-around-the-house watch. Everything functions well, except for the beep sound. Upon pressing the mode button, the beep is sometimes absent or becomes much less audible, then returns to its normal "beep" volume: beep, beep, BEEP, BEEP. The watch is relatively new, bought last year and worn at least once a week. I haven't been using its functions as extensively as the GW-5000. What do you guys think? Is this an easy fix?