$ darcs_flavour screened
darcs flavour is: screened (/home/gpiero/var/repos/darcs/screened/.cabal-
sandbox/bin/darcs)
darcs version is: 2.13.0 (unknown)
darcs compiled on Mar 20 2018, at 22:17:50

$ darcs ini --repo R ; darcs ini --repo S
WARNING: creating a nested repository.
Repository initialized.
WARNING: creating a nested repository.
Repository initialized.

$ touch R/filé

$ darcs rec -lam record --repo R
Finished recording patch 'record'

$ darcs push -a --repo R S                                                                        
HINT: if you want to change the default remote repository to
      /home/gpiero/tmp/darcs-test/S,
      quit now and issue the same command with the --set-default flag.
Finished applying.
Push successful.

$ ls *
R:
_darcs  filé

S:
_darcs  filé

$ darcs_flavour default
darcs flavour is: default (/usr/bin/darcs)
darcs version is: 2.12.5 (release)
darcs compiled on Jun 18 2017, at 20:43:30

$ darcs ini --repo T
WARNING: creating a nested repository.
Repository initialized.

$ darcs push -a --repo R T
HINT: if you want to change the default remote repository to
      /home/gpiero/tmp/darcs-test/T,
      quit now and issue the same command with the --set-default flag.

darcs failed:  Patch bundle failed hash!
This probably means that the patch has been corrupted by a mailer.
The most likely culprit is CRLF newlines.
Apply failed!

$ locale
LANG=en_US.UTF-8
LANGUAGE=en_US:en
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE=C
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=

Sorry, this also applies when the patch is created with darcs-2.12.5, so 
it's not a new issue (on the contrary, it has been resolved). Strangely 
enough, there seems to be no problem when using clone or send/apply 
instead of push.