2005 Renault Scenic check gearbox message coming up

Dear Team,

on occasions when driving there is a slight jolt of the car and then the check gearbox message appears, also after slowing down and stopping, on accelerating the engine revs are higher than normal to gain speed and also I find it will not change into fourth gear. If I stop and remove keycard then start the car again all warnig lights go out and message has gone and the car drives nomally, changes gear as nomal through the gears. This remains for a time then the symtons retun. I have had the car put on a diagnostic machine and was told that a camshaft sensor fault was recorded. I had the sensor replaced but it has not cured the problem. Can youy help

Regards J Coomber