Thanks for confirming that. That's what I thought and it likely is true--since the printer to which the labels were directed also turned out to be the default printer in that instance and it has only one bin. So it may not have been what the labels did to alter the default printer environment, but rather what they didn't do.
Perhaps it's the DEFAULTSOURCE=tray_ID line in the EXPR field--as suggested in Message #
951472 that Sergey referenced--that isn't working. Or perhaps I misunderstood the intent of Tracy Holzer's code. It seemed that command ought to direct labels to the proper tray, no matter how you obtained the tray ID (even without user intervention.) The last I heard yesterday though, the labels are still going to the default bin.