Mail Merge bug in LO 5.0.0.5?

Running on 64 bit Ubuntu.

I have an ods file I want to merge with a Writer document. Exchange Database works fine, and I’ve selected the Database in Data Sources. But I cannot drag and drop column headers into my Writer document. However I can drag in data from individual cells; interesting but not of any practical use to me.

Is it possible the cell references have got mixed up somewhere? Sorry, I’m not a programmer so can’t delve any further. Was not a problem in earlier versions of LO.

Any help greatly appreciated.

Thanks

RFO