Thanks for your bug report. The reason for this is that you have specified both 'o' for an ok button and 'n' for a yes/no/cancel button. You need to choose one or the other. While it would be possible to change this identifier to reject incompatible combinations of switches, it has behaved in this way ever since they were added, and changing it would likely break existing scripts where this is working. There are a large number of commands/identifiers that where created long ago where this is the case. In the end, it is up to the scripter to use the switches that they need and that work for them in the script that they are writing.