Tested with a simple data frame as input, i think it might be the Excel file itself.
workbook <- loadWorkbook(filepath, xlsxFile = NULL, isUnzipped = FALSE)
writeData(workbook, "Test1", al, startCol = 2, startRow = 5, colNames = FALSE)
saveWorkbook(workbook, filepath, overwrite = T)
But I get this :
Error in comment_list[[i]]$style[[j]] : subscript out of bounds