I’m running into a rather puzzling issue when running an experiment I’ve recently put online. The experiment involves participants playing a card game, with .png files used as the images corresponding to each card (all possible cards in a regular playing deck). A small but not insubstantial proportion of participants—exclusively Chrome users—have been reporting an “unknown resource” error at the beginning of the experiment, pertaining to one of the card images. The name of this image, AD.png (the ace of diamonds), is the first non-numeric file name in alphabetical order, but all the number cards should precede it alphabetically. It is the fifth-from-last resource listed in my “resources” dictionary. In other words, to my knowledge there is nothing special about it. I have had more than 100 participants successfully complete the task, suggesting that there is nothing wrong with the access of resources in most browsers, which is what is puzzling me (i.e., if it were simply a coding error of some sort that was going wrong for everyone, I would have some inkling of where to begin trouble-shooting).
I suppose my question, then, is: Has anyone else run into a similar problem? If so, did you identify the source?
Thanks in advance for any assistance.