carto - Dynamic content in infoWindow

I am trying to add some dynamic content to my infoWindow. The following code writes the string 'bar' to the element. However this works for the infoWindow of some points, but not for others (content is in variable, but not shown in the popup) in Firefox. Does not seem to work in Chrome at all. Any suggestions on how to do this? Edit: Surprisingly it works if an alert() popup is opened before the infoWindow.