Shamz_Q7

Hi guys, new on here. I have a problem with the Auto gearbox on my Audi Q7 3.0 tdi, 95k miles. Full recon engine and turbo 5k ago. When driving cold and putting my foot down gears seem fine. When engine is warmed up and I put it down a little, the car comes out of gear to neutral then slams back into gear again. What could be the issue? Mechanic said the gearbox oil was a little low but it was topped up again. So, any ideas anyone?? Appreciate any help!