Recently on custom workflows I've been getting this error message when trying to navigate to you a custom task form on a workflow. I had to enable logging to see it instead of "Unkown Error."
Only Content controls are allowed directly in a content page that contains Content controls. at System.Web.UI.FileLevelPageControlBuilder.AppendLiteralString(String text)
This message only occurs randomly and if I hit refresh a few times the task form will display. This message occurs in two custom workflows. I'll start testing the out of box workflows and see if this message comes up.
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