openxlsx conditional format: fine in Office 2013; error in Office 365

I create an Excel file using openxlsx, with conditional formatting, If I add one data bar, all is good; if I add two data bars, the file can be opened in Excel 2013, but I get a vague XML repair error from Excel 2016: "Replaced Part: /xl/worksheets/sheet1.xml part with XML error. Load error. Line 14, column 0.", and the sheet comes up empty.

The following code creates a sample of the two files. I'm trying to determine whether this is an openxlsx bug, or due to a change with the newer version of Excel. Any thoughts? I can do multiple instances of other conditional formatting (e.g.colourScale).

if (!require("pacman")) install.packages("pacman")
wb = createWorkbook()
sheetName = 'Test'
if (match(sheetName, names(wb), nomatch = 0)) removeWorksheet(wb, sheetName)
addWorksheet(wb, sheetName)
for (c in 1:5) {
    for (r in 1:40) {
        writeData(wb, sheetName, r+c, startRow=r, startCol=c)
conditionalFormatting(wb, sheetName, cols = 3, rows = 1:40, type = 'databar',
saveWorkbook(wb, 'OneDataBar.xlsx', overwrite=TRUE)
conditionalFormatting(wb, sheetName, cols = 4, rows = 1:40, type = 'databar',
saveWorkbook(wb, 'TwoDataBars.xlsx', overwrite=TRUE)