Rizvan Rafiul Haque Sowad

Hi Guys My Car is Toyota Premio 2002. Recently its not engage the last gear while driving. this is happening intermittently most of the time morning, and sometimes its shifting normally. If i stop the car and change the gears back and forth (P - L ) then the problem goes away most of the time. Previous owner said he did a gearbox oil change before i purchased the car but not sure about it. The gearbox oil level (engine running and Hot) is normal and the color is bright red, no burnt smell. do i need to change the oil ?? or anything wrong with a sensors or gearbox itself?? Really appreciate your help Thanks