This error can occur in the ESEF log from Tangelo or the Inspector tool. 

 

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It indicates that something is wrong with an element that is in your document. 

In the above case it indicates that a table row (TR) does not follow the expected content. The issue here is that there is a table that only contains header rows. This is often the case when a table should be connected to a data source, but is not yet. To fix this, look up the table in your document and simply add a new row that is not a header row. ESEF does not accept a table that only contains header rows as it's not allowed.