Random shifts into neutral

[SandyF]

My daughter has been complaining that her 2001 Camry (4 cyl, auto, 122K) has been slipping into neutral. Usually when she comes to a stop. I've never been able to duplicate the issue but I was in the car with her driving and it happened a couple times when she hit the brakes fairly hard. She moves the shifter to Neutral and back to Drive to reengage. I tried the same with no results. She says that some days it doesn't do it at all but on the days that it does, it happens frequently. She also says it is becoming more frequent. I had her take it to a mechanic where she lives. No problems were found. She has a "Check Engine" light on but the electronic diagnosis performed identified it as a catalytic converter issue. The car's maintenance has been consistant and seems to be in excellent condition, very tight and smooth and the transmission shifts fine. Any ideas on what the shifting issue is?

[Hajoca]

The shifting console between the seats should be checked.
Pry off the trim pieces and see if the track and detents (bumps) are worn out, or have shifted out of place.

[toyomoho]

Determine if the shift lever on the trans housing is moving in sync with the shift console, the two are linked by a cable. For the trans to shift into neutral the shift lever must move into neutral.

The other issues may be internal. The trans torque converter may not be working for a moment and thus the car does not move or a problem with the main shift valve.

Check the trans fluid condition (color) and level.