Maintain the same style line width

I have just printed a spreadsheet consisiting of 350 lines in length. It consists of 12 similar tables of yearly data. I painstakingly set each line in the tables to be 1.30 pt in width. When I closed out the program and turned it on again the next day all my lines were reduced to 0.05 pt. Can you tell me what I have to do to maintain the desired line widths?

Did you save the document as ODS?

I have found a problem with the borders (lines) when exporting to xls (but xls is not the LibreOffice native format)