Apparently they are not locking down. To lock them you push straight back on the tiller arm and once the rudder is in position, push down on the tiller arm and it should lock. Take a look at the cam and see if it is in the correct position to lock down. If it looks like a duck bill, then it won't lock down. So, take a large screwdriver and flip the cam so the duck bill is not showing. Then it should lock down.
If it doesn't, you may need to replace some parts. On our www.OnLineMarineStore.com we do sell parts to repair the rudder cams. You might need to replace the cam and push rod.
Rick