LibreOffice Calc displays dots across the sheet

I have LibreOffice for Mac. When I open a new Calc sheet, there are rows of dots across it. They extend to the limits of the spreadsheet, across and down. They are uniform. Every other row has twice as many dots as the intervening ones. There number of rows of dots is more or less, but not exactly, the number of rows in the spreadsheet. The number or rows does not vary with changes in zoom views, rather the rows get closer together or farther apart as you zoom out or in. Spreadsheets created before this problem started are unaffected (I can open them and there are no dots across the sheet). The dots consistently appear on a normal display and are also there in page break preview. The dots do not appear on a page preview. They do not appear on a printed page. They appear regardless of zoom level and whether or not anything has been entered in the spreadsheet. It only happens in spreadsheets, not in text documents. No other application on my Mac has these symptoms. I’ve been using LibreOffice for a couple of years and the problem is new. What going on and how can I fix it???

Duplicate of this one: LibreOffice Calc displays dots across the sheet - #3 by JohnSUN