sample a signal over long duration, edge and pulse trigger failure at low sample rate

I need to sample a signal over long duration, I set my DS09254 (firmware 4.50) to real-time single edge trigger mode, the trigger is a single pulse with width of 1 microsec. Scope will not trigger at low sample rate (1KSa/s), I had to set sample rate to 10MSa/s in order to trigger. The scope also fail to sense the trigger under pulse and glitch trigger mode.

On my old DS08104, the same set up works at any sample rate. Anyway I can get it work on the 9000 series?