Just setup a Dynamics 365 on-premises instance and had barely started customizing the Contact entity. After adding a new field and publishing I am unable to open the Editor for Contact entity form. I am also unable to access the Contacts view as it shows a message "An error has occurred". The error log has the following message.
System.Web.HttpUnhandledException: Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #4A9A4D93
1) Usually that happens when FormXML was corrupted during save, this is very rare thing.
2) To investigate:
a) download log file - it might give you some clue.
b) enable tracing on the instance and check the logs.
3) Possible fix:
a) Create a solution specifically for account entity. Only include corrupted form into it
b) download solution, open customization.xml file and find corrupted form. If there's not much customization done - simpleist thing is to wipe form out completely, if lot's of work done you might try to compare form against FormXML.xsd (found in sdk: SDK\SDK365\Schemas\FormXml.xsd) and fix corrupted element.
In future better never edit "managed" forms, instead create your own form and modify it. In that case you would at least have an option to delete the form, instead of trying to fix it.
Alternatively, take that form only from another environment & import it. Granular components can be moved as part of solution.
Guessing that you might have done removing the last field added & tried again.
This is my experience. When we upgraded to v9, account form got corrupted. On investigation, noticed that even preview from form editor failed.
Probable reason was a custom control (star rating) in form. Removing that solved the preview problem. But not the original issue. Reached out to MS, Simply “Publish All customizations” from Default solution fixed it.
