Glad to hear it works now.

I haven't really tried the deviation when losing the alignment yet, but in another thread we came to the conclusion that, from the numbers, you really lose it fast.
So I would recommend setting up the first DME update process just before starting the engines, so you will get a DME update on the first few miles of the flight where your workload is higher. Later, you can tune in the next station while already being in cruise or closer to it.
Over the ocean, you can't align and so you will lose the accuracy until getting in range of a high alt DME station. Should be around 200nm out from every coast, so enough time to be accurate over land then.

Maybe Lou can tell in more detail how they coped with the lost alignment. I don't think that they flew back to the departure airport then.  ;D
I would shout at the Flight Engineer or so, "that's why you are second officer only!, now I have to fix this".