Subliminal Stimuli (Images) don't show up when I run the experiemnt

I tried making an experiment with subliminal pictures but when I run the experiment, they don’t show up.
There is a crosshair (Text) with the following settings:
time (s): 0.0
duration (s): 1.0

Then the Subliminal Image followed by a mask:
time (s): 1.0
duration(s): 0.0167s (also tried: duration(frames): 1)

time (s): 1.0167
duration(s): 0.0167s (also tried: duration(frames): 1)

Then the experiment goes on with further text fields:
time (s): 1.0334

since I always got alerts with 20ms etc I changed to 16.7ms (because I have a 60Hz monitor)

macOS: 13.1
PsychoPy version: 2022.2.5
Standard Standalone
no alerts / error messages when running the experiment


I would always use frame when I like to achieve accurate and short presentation times. How did you tell that the images were not shown? 16.7 ms can hardly be noticed. In experiments using very short presentation times, I use longer presentation times during development and change those to the intended durations when everything is up and running.

Best wishes Jens