Should be triggered like what you said , but now in the firmware is : sample first then use software to trigger and display .
so also the Store Depth will effect the trigger , so even in single mode , the sample start time is random and the trigger time is also random that can not make sure you can catch the pules in one time ,if the sample store depth is smaller than a whole period.
what you use to see the files? can’t you load it back by use the DSO Nano 's Load file function? what displayed when you load back fail ? of you say you can not use a pc the see the wave that save in the file , you need to use the DAT2BMP tool to change it first for PC view.