Dev comment from linked issue: https://jira.k15t.com/browse/IEXP-3644
"The viewport macro should also be changed so it detects the viewport output mode not only by checking ContentTransformationContext.isRuntimeTransformation() because that obviously is true for v4 exports, however this certainly wasn't considered when the macro was created.
The check should be extended so the redirect is only attempted if it is rendered for viewport and not for runtime conversions triggered by v4 exporters."