I don't know, but I can offer a guess.  I use some fields from jobdb and also nsradmin dynamic messages to print out some stats - among the others sessions and, for example, to which device session goes.  From time to time, it will happen that I see session not being reported correctly and it is associated with blank (or empty) device. Few times I did a dump of these fields via nsradmin and I could confirm that formatting there gets broken for some reason and as consequence if you expect certain layout which you would use for parsing - you get unexpected results. Perhaps, maybe... this is the case here too.