Thank you for writing.
In our last release we added the column's data type to the information that is deserialized when saving the grid's layout. When loading this layout if the assembly of this data type is not loaded the exception occurs. .NET loads assemblies at the latest possible moment which is when a type of this assembly is instantiated and having a reference to the assembly does not load this assembly nor does working with its metadata.
We have this issue in our Feedback portal. You track the progress of this item, subscribe for status change alerts and add your vote/comment to it on the following link - Feedback item.
For now you can use the workaround suggested in the item.
I hope this will be useful. Should you have further questions, I would be glad to help.
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