Codes P1731 and P1732?

Hello, I have a problem and I hope you can help me so my vehicle listed above, 2 weeks ago I turned on the car in the morning and had a message “transmission fault” and when I put the Gear on R the car wont reverse and on the dash the R is flashing and when I put on D the car is not driving and the car stuck on 2nd gear and N and P works normal.
Then I took the car to the workshop and the mechanic said its the gear sensor in OBD shows that there is a problem with 4th, 6th and 5th, 7th gear error code p1731 and p1732 so I ordered new part and after he installed it the car drive normal for like half day then I got the message “transmission fault” again and I park the car and turned it off for like 30min then turned on and it worked good and no message and I drove it to the same workshop again and now he said its the same part and on OBD this time shows problem with 4th and 6th gear and then I turned the car on again and it worked good again and no message on the screen.