"xxx is null" when loading a component file
This error can occur when the OnAfterDeserialize code of a component file contains code to set values on an object in the component file, like CDF mapping components, and the full screen has not completed before the OnAfterDeserialize code is executed. This most often happens on very complex screens with lots of components or matrices that take a while to fully construct in memory.
Because this is a JavaScript timing issue, the best solution is to set the values on the sub-components in the OnBeforeDeserialize section by altering the incoming XML code. See the Code Snippet Setting CDF record ID in OnBeforeDeserialize for an example of how to alter the incoming XML.