So technically there should be no reason for such behaviour since we are not close to any throughput limit for the belt or inserter!

I do believe this must be a race between threads, once again, assuming belts and inserters run on separate threads!

That is not what is happening. Taking from ...

As far as I understand the belt mechanics, this is expected behavior. It's just because of the very exact belt simulation.
Underground entries and exits have only half the space for the inserter to pick up stuff. The other half is underground and not accessible. The inserter starts to look for ...

To be sure, what you consider the bug is, that an inserter can take faster from an underground belt outlet than inlet?


Well, yes and no! If that would be the behaviour then all 5 factories in the line would have shortage of items since they all pickup from the same underground type. The fact ...

Please find the link to a save.

https://www.dropbox.com/s/4bxu372u8yio66b/Test.zip?dl=0

I created 2 Low Density Structure lines. Please note the ever so often ingredient shortage for the line on the left for factories 2,3 and 4 compared to the one on the right which has no problems, the only ...

So, the situation is like this: I had 2 lines of 5 LDS factories 12 beaconed feeding from 2 lines of copper plates. Over time I noticed a slight decrease of LDS even though the feeding lines were backed up and Max Calculator showed me I should produce slightly more. Upon investigating I discovered ...