Hi Kate,
Did you run this experiment like this? There’s an incompatibility with PennController 2.1, you should upload version 2.0 to your project’s Modules folder
Regarding group distribution, note that by default, if multiple participants open your experiment at the same time, they will all be assigned the same group, resulting in imbalance. You can control group assignment by passing it as withsquare in the URL of your experiment
Jeremy