The torque converters give no trouble, it is the lock-up clutch in there that can be suspect. You don't have a model, mileage or history in your profile, so I can't be sure.
Some of the early 92 US models had a lining on the clutch that tended to flake off and block the cooler and the lube passages in the box. As you lost the high clutch followed by the forward clutch, I would think that it had the oil pick up screen in the box blocked by lining debri, Dropping the line pressure.
That said the SVX converter is stronger, so I would get them to drain the converter to see if there is any lining debri in there. If not use it, if there is don't use as it will continue to drop pieces into the new box.
I'd get them to reverse flush the cooler in the radiator to ensure that it is not blocked.
HARVEY.
