Daewoo frs2021ial beeps all the time?

Hi! I have a Daewoo frs2021ial, with a control display in the front, but no ice dispenser... A few weeks ago, it started beeping randomly!
It it the same beeping sound, as if the doors has been open for too long, but it is not regular, as in that case... When it beeps, the display changes between "lock on" and "lock off". Everything else is working fine, but the beeping is beginning to drive me crazy... Does anybody know a solution? Thanks!!