In Nav 2017 and 2018 you can be faced to this error “Object of type Query with ID 1850 could not be found” in several case, most common and user-blocking is when opening a released purchase order or purchase invoice :
This is caused by the standard extension installed in the base provide by Microsoft “Sales and Inventory Forecast”. Go to Extension Managment page and try to uninstall this extension. In case you already got some test and movment in your base you can have a internal error “There is already an objet name […] in the database”
When uninstall nav app with default command, table data provide by this appliation is keeped in the database. This MS extension probably have code on uninstall event that provoke this intenral error with table data. You can bypass this error using following powershell command with administrator rights :
Uninstall-NAVapp -Name "Sales and Inventory Forecast" -ServerInstance "DynamicsNAV110" -Force -DoNotSaveData
This avoid the SQL error with -DoNotSaveData instruction to uninstall this buggy extension and let you open purchase documents again et voilà