Trigger function

I have a notebook with Windows 7 and attached a PCGU250.
The 2 probes are connected to a pwm signal with about 5 V.
I set the trigger level on ch 1 to 3 V positive slope. I pressed trigger_off and Run. The mode is “running”. On the screen i can see the recorded signals (always moving a little bit horizontally); that’s perfect. When i change the pwm-width, this is also displayed well on the signal-screen. So this kind of signal recording works for me.
Now i press Trigger_on. The mode is “trigger on”. The horizontal moving stops but the signal-screen does not freeze. When i change the pwm-width, either ch1 or ch2, this change is seen on the signal-screen.

Another use case is: i set the pwm width to 0t the scope cannot detect a trigger. After some seconds the mode chages from Running to waiting fro trigger. When increase the pwm width the mode changes to running.

In any case, when the scope triggers, i would expect, that the display screen freezes and i have the changes to investigate the recorded signals. And this is not possible.

My question is: Is there a misunderstanding of the trigger process or is there a software mal function of the scope?

best regards