Cellar is having network issues on some node. Some requests are failing, both requests to GET resources as requests to send resources.
We are investigating the problem
EDIT 19:35 UTC: The problem seems to be gone.. It may be due to a maintenance operation made on the Cellar cluster which shouldn't have caused this. This maintenance has been done multiples times without problems. We will keep an eye on the cluster when this maintenance starts again, probably tomorrow.