Updater still misses some updates when two updates are done very close to each other, esp. by script. Probably because some servers see only one update in the RC stream and when they load the data it may be still the old one. It may be possible that this is because of caching - on the first update, the page is cached, and the second request gets the same version. We may want to add check that we do not fetch revision older than the update indicates.
Example:
this update:
https://www.wikidata.org/w/index.php?title=Q23753838&diff=499932595&oldid=499932539
is missing on wdq23, which has last revision as 499932539.