Polo auto 2005 gearbox speed sensor

[Caddy2156]

Hi
Have a vw polo 1.4 s 75 auto 2005
Need help engine management light is on..
I get code p0715 powertrain input/turbine speed sensor circuit.. on my obd scanner. Can remove code but keeps returning.
Have taken to 2 different garage's
One garage gave code 00297 gearbox speed sensor (g38) the other told me gearbox has gone..
Had oil replaced in gearbox which is 4 speed
The car and gearbox has been running fine for 2 months now!! Just need engine management light off
Any ideas on who or how to fix?

Thanks