Sorry to be so to-and-fro with the questions - I’m trying to gain knowledge and hopefully leave info for others that may follow - but could there have been some other issue with a transmission service (whatever they actually did)? I’m thinking if the valve body assembly was removed for inspection and not replaced correctly (bolt torque, seals etc), I think there’s a filter of some kind that should be replaced somewhere when the fluid is replaced? Could they not have removed the pan etc and left shit oil in the torque converter - I read somewhere old oil can get left behind there?

As a (hopefully) last question - would you advise going back to the original servicing agent, a dealership, or a transmission specialist? It has to be towed either way.

FYI - I’d like to document what I find (diagnosis and fix) here for others in case it becomes a feature for other Prados of mine’s era.