Randomly tiny initial dialog box

URL of experiment: https://run.pavlovia.org/ps2/acquiescence2/html

Description of the problem: I’ve created an experiment for a project a few undergraduate students are completing, and when they were testing it on their laptops one of them had the bizarre issue of the initial dialog box (in which the participant number, session number etc. are entered) showing up almost illegibly small. This student was using Chrome on a PC, whereas the others were using a variety of browsers on Macs. I’ve never had such a problem on PC or Mac, in any browser, so I’m struggling to come up with a possible cause. Any suggestions as to why this might be occurring would be appreciated.