I'm sorry if i was wrong.

I just have the problem to create xlsx file with exceljs.

Ex) below is pseudo code.
case OK:// All border shows correctly.
getCell("A1").border = border_all(top right bottom left);
getCell("A2").border = border_all(top right bottom left);
getCell("A3").border = border_all(top right bottom left);

case NG: // A1's border only shows.
getCell("A1").border = border_all(top right bottom left);
getCell("A2").border = border_all(top right bottom left);
getCell("A3").border = border_all(top right bottom left);
worksheet.mergeCell("A1:A3");