Same field values repeating when displayed in table

Hi 

This is similar to Solved: Text value is repeating - Microsoft Power BI Community, but the solution there does not work for me.

I have a section name field that serves as a header for a table, but a couple of the fields are repeating and I cannot understand why. 

I assumed the text was slightly different for the section name records, but I have run an update statement at the source to ensure that this is not the case. I am new to PowerBI and did not create the report - I am just trying to remove these duplicate columns.

This is the source table (not all fields, but I dont think the others are relevant), and the table displays in PowerBI are below, as can be seen ShortName displays unique values as expected, whilst for SectionName, "Self Guided Learning" and "Additional hours.." are repeated. Another interesting thing is that when clicking the header to sort display order, the order is incorrect for the SectionName field as well.

Source Data:

This is how Section Name displays:

This is how ShortName displays

Any ideas/suggestions would be greatly appreciated, the column is not used for sorting or as a key.

Regards

David