Assuming the gearbox is a ZF 5HP24. A quick look at RAVE describes only P codes for this model and thre are 2 possible OP sensor codes, P0720 & P0721, both of which are implausibility codes NOT circuit codes, in fact I can find no DTC reference to speed sensor cct. codes, this may be a clue.

P0732 however is a 2nd gear ratio error, this would be consistent with the symptoms you have as a ratio error (slip in any gear) will flag both ratio and speed sensor implausibilty codes.

Summary: Poor 2nd gear engagement can and will cause these DTC's to set. You need to consider that there is some kind of internal gearbox issue affecting 2nd gear, hydraulic controller and servo leak off rates would be the most likely culprit in this case. HTH.