Torque converter faults after engine out - engine in event

[jempot]

I recently had the timing chains replaced on my VE V6 (2008) which required the engine to come out for cleaning (due to excessive sludge). This meant the engine was separated from the box. After the works were completed, I am now getting the 'Stability Control OFF' fault along with the P2764 'Torque converter clutch pressure control solenoid control circuit low' code intermittently causing erratic shifting. It shifts perfectly when the 'Stability Control OFF' fault does not appear.
I've never split the engine from the box before so looking to others for any suggestions on what might have occurred that could be causing this to suddenly appear. The mechanic who performed the work is adamant that there was nothing touched that could cause this and that it suggests a problem with the box. Whilst I'm sure he genuinely believes he hasn't done anything to cause this, I think it's a huge coincidence that this fault has only started appearing right after these works.
Is there anything that could either have been bumped (torque converter?) or stretched or pinched (looms?) during the re-attachment to the box? Excuse my ignorance if my examples are not valid. I'm just getting desperate!

 

[DJ_Cosmic_Fire]

If the Torque Lockup Convertor is not slotted onto the transmission pump extension spindle in the proper three stages, then all types of issues will present themselves when driving. Take your car back & they will have to pull the transmission out, redo it properly & make sure all the electrical components are in working order - for free. If you have absolute proof that it was running perfectly before taking it to them for the timing chain job, then simply present the last service report or a scan tool diagnosis of the car's main computer which will have logged the codes to prove that they have done something to upset the car's normal operation. IMO it does not make any sense to pull out the engine to replace the timing chains & tensioners, it's a straight forward job that is done with the engine left in the car. The notion that they'd pull out the engine due to excessive sludge is complete overkill & would have cost you a small fortune. The entire kit is 700 & will take a day DIY to complete the swap over, which would include cleaning & replacing any other parts that need attention whilst getting the job done.

 

[jempot]

If the Torque Lockup Convertor is not slotted onto the transmission pump extension spindle in the proper three stages, then all types of issues will present themselves when driving. Take your car back & they will have to pull the transmission out, redo it properly & make sure all the electrical components are in working order - for free. If you have absolute proof that it was running perfectly before taking it to them for the timing chain job, then simply present the last service report or a scan tool diagnosis of the car's main computer which will have logged the codes to prove that they have done something to upset the car's normal operation. IMO it does not make any sense to pull out the engine to replace the timing chains & tensioners, it's a straight forward job that is done with the engine left in the car. The notion that they'd pull out the engine due to excessive sludge is complete overkill & would have cost you a small fortune. The entire kit is 700 & will take a day DIY to complete the swap over, which would include cleaning & replacing any other parts that need attention whilst getting the job done.

Thanks for your response. Just curious whether the box can still be bolted back up to the engine if this was the case?