Years of experimentation and we may have finally settled on the perfect setup...

​Problem
A custom Document Information Panel (DIP) fails to open and returns a schema error.  The following screenshot is an example of where a once functioning DIP fails to load because of metadata that has been added incorrectly to the content type.  The problem presents in SharePoint Online but is likely to be evident in an on premise implementation also.
​
Cause
When a DIP is customised it is ‘hard-coded’ to understand the metadata that is expected to be supplied by the library at runtime.  Even the ordering of the fields within the library seems to be significant.  When fields are added to a content type it causes the rendering of the DIP to fail.  In this specific example two publishing fields had been injected into the content type by an external process.  We are yet to determine what this process was but we know it wasn’t manually added.
As can be seen in the screenshot the fields that caused our issue were publishing fields whose display names are Scheduled Start Date and Scheduled End Date.

Solution
Switch off scheduled publishing
The two fields that are causing the problem are ‘sealed’ fields and thus cannot be manually deleted. In order to remove them the following process must be followed:

In the document library settings, go to versioning settings and set the following properties:

• Content Approval – Yes
• Versioning – major and minor

So, it turns out running a business is quite a big deal - it takes a lot of time, all the time!

My own once, religiously updated blog has gone a little stale of late.   It's also time the whole company got on board so...

New website, new focus.  Resonate IT are going to try and be a bit more focused on keeping a blog going between the team.  That blog will be here ;-)

For anyone wanting to get to the old blog, follow this link to find happiness: https://andynoon.wordpress.com