RPPreprocess expects the md5 checksum of the file to change after processing; if it does not change, RPPreprocess assumes something failed and will error out.
To tell RPPreprocess that the unchanged md5 checksum is intentional, you will need to create a ".result" file in the SUBMIT/ directory with the same name as the submission.
Submission file = 20150601112233444Chrzaszcz
.result file = 20150601112233444Chrzaszcz.result
This file should only contain the text result=0.
You can create the text from the batch file with the following command
(this assumes that the file path ($FPATH) and file name ($FILE) were passed to preprocessing as the first and second arguments respectively):
<nul (set/p x=result=0)> %1/%2.result