Hi @MFB, I believe this is an issue with your conditions file. The issue is because PsychoJS is attempting to draw an undefined image. We have had issues related to empty trials being added to trial handlers, probably relating to having empty formatted cells in your conditions file (i.e., they had information in the cells, but this information was deleted.). This is your trial handler with empty trials:
I have already added this issue to GitHub, but will add to the post as this is a recurring problem.
You can fix this by copying only the entries from your conditions file into a new, blank conditions file, being sure you only copy those rows with information, rather than selecting whole columns.