Regex plug-in and error loading design mode

Hi, I've discovered that if I have a user interface with a regular expression on it (from the Appian Regular Expressions plug-in) the page won't load into design mode.

Has anyone else discovered this - or perhaps worked on a work around?

relevant SAIL code:

                      a!textField(
                        label: "BSB Number",
                        labelPosition: "ADJACENT",
                        placeholder: "000-000",
                        validations: if(
                          regexmatch(
                            "^\d{3}-\d{3}$",
                            ri!allowanceApplication.payeeList[local!selectedPayeeIndex].bsbEFT
                          ),
                          "",
                          "Please enter BSB in the format 000-000 "
                        ),
                        value: ri!allowanceApplication.payeeList[local!selectedPayeeIndex].bsbEFT,
                        saveInto: ri!allowanceApplication.payeeList[local!selectedPayeeIndex].bsbEFT,
                        required: true
                      ),

The error message when switching from Expression View to Design View is: