I think it's a bit of a political move here, the EU have let some 150 shipments leave their shores already from AZ & Pfizer, but no answers as to why they're stopping this one. EU seem to be stockpiling volume at the minute due to a low take up rate, as of last week France had used around 16% of their 1.1m doses, Germany just over 20% of 1.45m doses, Italy 20% of 1m doses, and Spain with 30% of 800k doses.
I don't see how 250k is going to impact a delivery schedule when it's clear that some EU countries are doing a very poor job in terms of using the doses available.