The 'line out' error on my DR occurred again, for no particular reason. Actually, it started to happen only about a week after last time I posted about my DR 'fixed itself'.
Of course the right thing to do is to talk to iRex and send my DR to the Netherlands, but I hated to part with it for a few weeks. So I 'fixed' it myself this time.
I observed that if I put gentle pressure around the point on the top of the bezel where the bezel meets the line in problem, then the line out problem vanishes. I guess this could be some kind of problem in soldering or something similar. So I put a clip on that part of the bezel, and now I can use DR with no line out problem.
So far so good, except that I'm not sure whether this is a good enough fix or only a stopgap which will fail eventually. Perhaps I'll have to send it to iRex eventually, when I'm less busy and before the warranty expires.