I discovered and resolved the problem myself. It was caused by bad syntax in the following segment on the trial “Rueckmeldung”:
There need to be quotation marks around the word “final”.
As I described above, this error caused the trial to not be displayed at all; it also seems to have caused the following trial (“Dank”) to not be displayed, both of which without an error message in the debugger. I could not find any additional mistakes in the code of trial “Dank”.