STRING and duplicating the item originally added to the cell

STRING and duplicating the item originally added to the cell

I am having problems with the ZOHO spreadsheet adding STRING and duplicating the item originally added to the cell
I have set the cells to text after removing all the duplicate data and then saved the file. Each time i open ZOHO an additional 
STRING5-31007 is added to the cell.
below is an example 
Any ideas?

5-31007STRING5-31007




5-31007STRING5-31007STRING5-31007STRING5-31007