Is changing the sensor the solution to gear not changing?

[shrek]

once or twice when i couldnt change gear to 1st my mechanic said it can be malfunctioning of speed sensor. but this happened only 2 times should i still change it?

[ifty]

In my suggestion wait till it repeats.

[gearahmed]

I am not really sure why or how that could have happened but I would follow ifty's suggestion which is to wait for it. Anything you were doing unique when those 2 instances happened?