I am upgrading an existing web site from v8.17 to v9.0.1 The SQL Express database was updated via the v9 implementation process and was then run using 'dotnet run' without errors. Save and Publishing of existing or new nodes creates no errors. The v9 website was published using 'dotnet publish' without errors. A local IIS website was created and pointed to the published website folder. Folder permissions were set to full for the AppPool object, NETWORK SERVICE and IUser. The AppPool was updated for "no managed code'. The IIS deployed site displays data and allows new nodes to be created and saved (not published) or deleted. When updating properties and performing a 'Save and Publish' action, the error 'Server error: Contact administrator, see log for full details. Object reference not set to an instance of an object.' is displayed at the bottom of the screen in red. When checking the /umbraco/Log the node shows as published with no error. When checking the SQL Server logs, there is no error shown. I created a new v9 blank database and published it to IIS and the above error does not happen, so I think it has something to do with the database. When comparing the databases using SSMS I dont see any obvious differences. Any help regarding where to find more detail on the error or where to look in the database for a possible problem would be appreciated.

PS: I had a similar problem when upgrading from v8.14 to v8.15 but the issue was solved in v8.16 - I am not sure what umbraco code changes may have occurred between these versions, but maybe that would be helpful to know.