New error when setting up preload queue for some participants but not others

URL of experiment:

Description of the problem: I have been running an experiment on pavlovia for the past 2 months and have recruited 200 participants with no problems. However, in the past few days, I’ve had 3 participants message me saying that they are getting this error message:
"Unfortunately we encountered the following error:

when setting up a preload queue
unable to download resource: images/Sn118.bmp (images/Sn118.bmp)

Try to run the experiment again. If the error persists, contact the experiment designer."

The experiment works completely fine when I try it locally and when I run it online, and it seems to be working for most people except for a select few. My image components are set using a conditions file ($stimFile). Any help would be appreciated!