In the save you'll see I'm standing next to a terrible hack which builds green science from robot logistics. Note, in particular, the requestor feeding the iron-gear-wheel assembler just to my right. If you open up the UI for that requester chest, and hover the mouse over the request slot for iron plates, you'll see that
- There is a general shortage of iron plates in my network
- The checkbox for "request from buffer chests" is checked
What I believe is happening is that somehow requester chests with "request from buffer chests" checked are effectively given a lower fulfillment priority when scheduling logistics deliveries of scarce items in busy networks, either because they are in a different queue which starves for deliveries in a shortage, or, if there is just one queue/list, then due to some glitch in the code which normally slides the fulfillment window in a loop over the list of requesters (which would normally ensure that in, a shortage, everybody gets a little bit), causing starvation of some (but maybe not all) requesters configured to request from buffer chests. It might be a build-order thing; these chests are among the last to have been built in this network.
[Moderatrivia: the above is a word-for-word repost of a (misplaced, sorry for that!) previous bug report that I believe Kovarex dismissed in error (which in turn led me to falsely believe my report might be based on a faulty assumption, but I no longer think so... Sorry, for such confusion ... it's like a really boring episode of "Three's Company"). Anyhow I'm pretty sure he interpreted the above as "I have this buffer chest and it's starving" but it actually says: "I have this requester chest and it's starving". If I'm just being thick (quite possible) I'd at least like to figure out where I lost the plot.]