sprintf error when using the openxlsx datavalidation for a list

Question

I'm trying to create an R code which can automatically make excel sheets with drop down lists. I'm using the openxlsx package for this with their Datavalidation function.

When I run the file for each individual line (so with ctrl+enter) the excel file works. However, when I run the whole file at once then my excel file gives an error that it's unable to open the file.

I keep getting the same error though, and I don't know how to fix it.

Warning message: In sprintf("<x14:dataValidation type="list" allowBlank="%s" showInputMessage="%s" showErrorMessage="%s">", : one argument not used by format '<x14:dataValidation type="list" allowBlank="%s" showInputMessage="%s" showErrorMessage="%s">'

Warning message: In sprintf("<x14:dataValidation type="list" allowBlank="%s" showInputMessage="%s" showErrorMessage="%s">", : one argument not used by format '<x14:dataValidation type="list" allowBlank="%s" showInputMessage="%s" showErrorMessage="%s">'

This is currently my code.

wb <- loadWorkbook(existing_file)

#Add sheet
if(!"Dependent" %in% getSheetNames(existing_file)){
addWorksheet(wb, "Dependent")}

# Add worksheet "Drop-down values" to the workbook
# Hide the worksheet
if(!"Drop_down_values2" %in% getSheetNames(existing_file)){
addWorksheet(wb, "Drop_down_values2", visible = FALSE)}

#create variables in R
items <-  dependent_table$Item
value <- dependent_table$Value

# Create Customers dataframe
myList_df = data.frame("Items" = items, "Value" = 
                         value)

# Add Customers dataframe to the sheet "Customers"
writeData(wb, sheet = "Dependent", x = myList_df, startCol = 1)



# Create drop-down values dataframe
myList_dropdown = data.frame("Values" = value)

# Add drop-down values dataframe to the sheet "Drop-down values"
writeData(wb, sheet = "Drop_down_values2", x = myList_dropdown, startCol = 
            1)

length_rows = length(value) + 1
# Add drop-downs to the column Gender on the worksheet "Customers"
dataValidation(wb, sheet = "Dependent", cols = 2, rows = 2:length_rows, type = "list", 
               value =  sprintf("'Drop_down_values'!$A$2:$A$%d", length_rows))


# Save workbook
saveWorkbook(wb, "PeterExcel.xlsx", overwrite = TRUE)

I've tried changing the sprintf to paste or paste0, but none of them worked. I also tried removing the length_rows completely by simply saying range $A$2:$A$7, and I still got the same error.