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Do you have zone valves ?
i guest .i brought this house 3yrs ago and don't have any idea how or where my system works. does my system have a box where the water comes in to 1 box and then splits to each zone or do they normaly have they have the vavle at the start of each zone.. can a valve be able to leak and create a leak strong enough to allow the sprinkler head to dribble enough to raise the head up and leak. this is what is happening ...i think.
Most of the time there are zone valves and they are in a round or square plastic box in your yard. They are most of the time before that zone. It sound like there is foreign debris in the zone valve and this is what is causeing the head to leak. You will need to try and locate this valve box and disassemble the valve and clean it.
If you can not locate this zone valve box, most sprinkler companies have equipment to locate these boxes.