This is solved. The script was referencing 'CustomVariables.csv' but the actual file name under the 1.BaseVariable folder was 'Custom.Variables.csv' (dot[.] present between the word Custom and Variable). I created a copy of the 'Custom.Variables.csv' within the same directory and renamed it to 'CustomVariables.csv' (as referenced in the script). I reloaded the app and now no errors appear.