I have encountered the problem you described in this reply: some of my participants saw the “Preloading, please wait” screen and was stuck there for a while before they could proceed. Before I published the experiment, I made sure to try and do all the groups once to make sure there wasn’t any technical issue. After getting reports from some participants, I checked the csv file and the zipped file to make sure the names in the csv file corresponded to the audio filenames.
Would this message trigger from the participants’ end?
Here is the experiment link.