Variable InterStimulusInterval

If you run the following (very short) experiment:

ISI.psyexp (20.1 KB)

with the following (very small) File:

ISI.xlsx (21.8 KB)

An error pops up in the end. This error is unrelated to the Excel File, but disappears if I take out the Excel file from the conditions and set a fix ISI duration (which is what I don’t want). Can somebody explain me what’s causing the error?

Update: I found an option (see below, without Excel), but only if implementing the ISI in a separate Routine. Is it possible to implement the ISI in the same Routine as the stimuli, while Force End Key remains ticked for that same routine in the builder? I would appreciate any solution; otherwise the number of my routines in my experiment (15) will be doubled (to 30) just for adding an ISI routine after each stimulus routine…

ISI.psyexp (20.1 KB)