Program crashes after inserting new routine

Windows 10
Psychopy v.2021.2.3

I am learning to use Psychopy with Builder and trying to build a perception experiment, which is based on the presentation of acoustic stimuli. The basic structure includes:

  1. a sequence of text at the very beginning as introductory information about the nature of the experiment and how to respond to the stimuli
  2. and a task.
    (I started building the experiment with the first task, and only in a second time I introduced a new routine before it containing the multiple texts.)
    The first task consists on the presentation of images and sounds, which run sequentially in order to give the idea that each sound is associated to an image. I tried to run the first task and everything went fine.
    After introducing the texts as the first routine before the task, I tried to run the entire experiment (both routines): on the screen appeared the window with the “participant” and “session” entries, then the loading symbol and a grey screen for about 2 seconds. Otherwise, the experiment interrupts (a crash?) almost immediately without even showing the first routine.
    I face the same problem also when I try to run the single routines - which surprises me, because at the very beginning I could at least run the main task.
    I can not find the reason of this phenomenon: I also opened a completely new Builder-window and tried to build again the first routine: it runs. Now I ask me why the very first experiment does not function.
    Has anyone faced a similar problem? Could you give me any suggestions?
    Many thanks in advance!