I am now using version 184.108.40.206 of the CAA File library, but I seem to be having the same issue (or maybe a different one) with using the DirCreate function block
When trying to create a directory, I get ERROR_UNKNOWN (5110), if the directory already exists. I guess I would expect EXIST (5105). This seems to be happening with the xParent option both true and false.
There's not a lot of documentation for this library. Are there any other things I should be considering?
I use CAA File 220.127.116.11 with CODESYS Control Win V3.
I test your case, and DirCreate return error EXIST (with any value for xParent).
So I think it was fixed or it's OS-dependent bug (maybe you test it on Linux...).