Its like my Bosch GOF 1300CE 1300w. What causes it to "unlock" is vibration while routing notemment if its mounted on a router table. I guess your router is as sensible as mine while routing.Its damn annoying to lose presetted depth while routing. Try dismantling it, clean the rods that supports the foot, but DO NOT add oil/grease/CRC, other wise your back there again. Try also to readjust the locking system so it gets tighter when you lock it. I think this is ths cause of slight wear on the locking system.