Sounds like my mum's backyard. There's one zone with a pipe end that looks like it's never been closed off and the water just gushes out so I leave that one off. Given it's one that runs along the fence and the ones in the lawn spray out that far anyway, it's an unneeded zone.
Of course if' she'd stop running over the popups with the lawnmower it'd make my job a lot easier...
Ah lawnmowers and pop ups... the joy. Had to replace two the last time a helpful soul mowed my lawn for me.
I tried a few things unsuccessfully, before just closing the valve a bit. Somehow seems to have done the trick. Also fixed a hole elsewhere and got the retic working better than ever before.