CRAN check: '\R' is an unrecognized escape in character string starting "'D:\temp\R"

I'm trying to update a package on CRAN, but I'm getting a warning on their automatic check I can't reproduce in R CMD check. These are the last lines of the log file:

   * checking re-building of vignette outputs ... [0s] WARNING
    Error(s) in re-building vignettes:
    Error: '\R' is an unrecognized escape in character string starting "'D:\temp\R"
    Execution halted

R CMD check passes with no errors in my computer for both Linux and Windows versions and I'm unable to find where is "'D:\temp\R" being used. There is no file path written in the package vignette at all.

How can I figure out where exactly is the error happening and fix it?

I'm aware how the backslash causes trouble in Windows and most similar questions are related to that, while my problem is at finding out why CRAN did this even when I didn't use file paths at all.

Solution

It seems like it was a CRAN problem as mentioned in the comments. I just received an e-mail as if my previous submission was fine, without sending a new form.