solves the issue:
--- updates.orig/60upgradeconfigfiles.pl 2018-09-03 09:58:45.911804203 +0200 +++ updates/60upgradeconfigfiles.pl 2018-09-03 09:59:36.420699451 +0200 @@ -31,7 +31,7 @@ next if (! -f $oldname); # does not exist - skip - already (re)moved my $newname = "$bakdir/$file"; $! = 0; # clear - rename $oldname, $newname; + move $oldname, $newname; if ($!) { push @errs, ["error_renaming_config", $oldname, $newname, $!]; } @@ -57,7 +57,7 @@ next if (! -f $oldname); # does not exist - not backed up my $newname = $inf->{slapd}->{config_dir} . "/" . $file; next if (-f $newname); # not removed - rename $oldname, $newname; + move $oldname, $newname; } return @errs; }