We are trying to use ListItem's REST API ValidateUpdateListItem call to update fields of an item in a document library without causing new versions to be created. We can generally make this work, but we have Fields of type Note to hold multiline text longer than 255 characters. When we use ValidateUpdateListItem to write these with strings longer than 255 characters, using the InternalName of the field (e.g., My_x0020_Internal_x0020_Name), we get errors indicating that the text is too long.
We are able to write these fields via a MERGE request to the ListItem with exactly the same field name and value in the map provided as the body of the MERGE request.
Any ideas for how to write long text fields via ValidateUpdateListItem?