I suspect that WDQS updater may be reading older RDF data than the latest edit. I.e. I am getting log messages like this:
20:53:35.953 [update 1] WARN o.wikidata.query.rdf.tool.rdf.Munger - Stale revision on Q5576287: change is 797238340, RDF is 683087222 09:23:21.076 [update 4] WARN o.wikidata.query.rdf.tool.rdf.Munger - Stale revision on Q132990: change is 797548413, RDF is 791644240 20:14:17.327 [update 8] WARN o.wikidata.query.rdf.tool.rdf.Munger - Stale revision on Q15277881: change is 802706968, RDF is 736343558
Which means that the Updater knows that last revision was 802706968, and yet when requesting RDF via https://www.wikidata.org/wiki/Special:EntityData/Q15277881.ttl?flavor=dump it got revision ID 736343558.
This is problematic since this means whatever data is updated between 736343558 and 802706968 is lost. It is not result of the caching, since the request has special URL addition that is different for each request (timestamp-driven).
I wonder if there's any way to ensure we get the freshest RDF and not stale information from Wikidata.