Command line:
/usr/bin/php5 /srv/mediawiki/multiversion/MWScript.php extensions/Wikibase/repo/maintenance/dumpRdf.php --wiki wikidatawiki --shard 4 --sharding-factor 6 --batch-size 1500 --format ttl --flavor full-dump --no-cache
yields:
[failed-to-dump]: Failed to dump Q12129 (Value must be at most 127 characters long.)
This didn't show up in Monday's JSON dump, so this is probably related to one of the recent edits:
https://www.wikidata.org/w/index.php?title=Q12129&type=revision&diff=635245443&oldid=631529032