Firsttime user so I apologise if this is in the wrong forum.

I recently had an expensive service by our Local Holden dealer in Australia.They performed a log book replacement of timing belts as per the service book with 110,000km on the clock.
All good until a week or so later when the car starts going into limp mode.
No power and stuck in 5th gear (auto)?. As the car accelerates there is a hard clunk from the transmission and the car goes into limp mode.
If I stop/start the car again, sometimes it would clear the problem. I get the traction control warning light come on and the emissions warning light.
The warning light with the spanner comes on at times as well meaning its detected a fault in the electrics for the transmission.
Got the car back to the dealer and they said they couldn?t find the fault even though I had given them the P1895 code from the ODBII scanner.
The car kept having the same problem. Sometimes the car wouldn?t even start.
With the intermittent problem I purchased a basic scan tool to check the error code.
The car keeps getting a P1895 error.
If i clear the error the car will start and is fine but it?s unpredictable as to when it will reoccur.
Sometimes a week sometimes a day. We have stopped driving it and this is driving me mad.
I have read many other forums with the same issue but each time the problem is sorted to some extent but it seems that the solution is always different.
My feeling is something has happened when the timing belts were changed.
Not being mechanical is frustrating me as I believe this problem is solvable.
Could this have something to do with the Crank angle sensor and some sort of "relearning" process given they have been in this area of the motor?
Im about to change the transmission oil as there have been posts about this helping and fixing the problem.
The dealer said the transmission oil was fine
The car has been serviced since new by Holden who badge the Opel? as a Holden in Australia.

Any feedback appecited.