Error on mobile: undefined is not an object (evaluating 'Da.pages.$btnNext.on')

[NickGIS]

I have a webbapp version of a survey which is working fine on Chrome and Firefox on a Windows desktop, but I get the following error when trying to use Safari on an iPhone (iOS):

undefined is not an object (evaluating 'Da.pages.$btnNext.on')

Does anyone know what this error means, or how I might be able to fix it? Thanks

[ZacharySutherby]

Hello @NickGIS, 

Is this issue still reproducible? If so would I be able to obtain a copy of the survey for testing on our end? What version of iOS is the behavior observed on? 

[WarwickHehir]

I have a similar issue in both Chrome and Safari on iOS 12.5.7.
When I close the "Error: Initializing form..." pop up there is no next button to progress the survey.  Full error message is "undefined is not an object (evaluating 'Is.pages.$btnNext.on')"

[WarwickHehir]

Also the heading of the survey group is showing some of the formating tag such as <center> and </center>