When using user-defined emulation, when you select a new data file in the data selector and click OK, it reverts to Line Printer emulation. If you don't happen to notice this, you can waste a lot of time wondering why the data appears differently. Just a small thing perhaps but it has caused me some problems before I realised what was happening.
Why is this a bug? well apart from being annoying, it doesn't happen in V6.2. In 6.2 the user defined emulation remains selected when you change the data file and I know of applications that rely on this behaviour.