Land Rover Discovery 2002 both s and m lights are flashing indicating electrical transmission problem also its sticks in 3rd gear then if its cut off for awhile it resets itself what switch?

I assume this is an auto? Get underneath and with a struggle you will see a cable connector block that feeds the autogearbox switch. It will be hidden behind the exhaust on the passenger side. Just above it is a tube the AC drain. It lets water go all over the connector block and that then corrodes the connection and the voltage loss causes a the M and S lights to flash and limp home mode. Another cause of this can be a tired battery. This can also create M&S flashing lights. Check battery coltage. Should be 12-5V + at rest and 14.5V + when engine running.