I suspect the image sequencer is failing to close the stream because of a failure. Can you try it with one of our test images? At least it will tell us if it's image-specific. Would you mind logging this so that we can change the sequencer to always close the stream? We'll fix this in the 3.1.1.Final patch release (which I've tentatively scheduled for 2 weeks from today, tho we're flexible on the date).
UPDATE: I've already logged this as MODE-1762 to be slightly more general against all the sequencers, just so that we check them. No need to log another one.
It works if I use minimumBinarySizeInBytes=4096, but if I lower it to 1024 it also hangs again...