Had a feeling it wasn't a real regression, in that it isn't a resolved bug reappearing: the original bug, which was confirmed as such by kovarex fixing it, was "inserters try to insert ores into furnaces smelting steel , creating deadlocks". The behaviour now is: "inserters try to insert ores into ...

Summary:
Inserters sometimes try to insert ore into a furnace already containing iron plates.

History:
Something very similar was already posted before, and fixed, but the fix seems incomplete or has regressed:
Original report:
https://forums.factorio.com/viewtopic.php?t=8275
Reported as fixed ...