Im forced to report this bug here despite there being a chance that this is caused by the "Exotic Space Industries" Modpack https://mods.factorio.com/mod/exotic-space-industries because they have locked the ability to report bugs to them.
Whats happening is that sometimes when inserting from a furnace in to a chest it says "Waiting for source items" and it refuses to work until i do something to update the inserter such as toggling the use of filters and then it works again for a while despite the chest having free space it could insert to.
A second thing which i noticed also but im not sure if its a bug is that unlike the spoiling items from space age and most other mods the hot plates dont spoil while in the furnace, tho i dont know if that mismatching behaviour could have something to do with the above mentioned bug.

I cannot do anything about the first thing you describe.

The second thing is intended. There is the bug/feature in Factorio that the spoil timer starts when the recipe crafting starts. So when the recipe is finished, the duration of the crafting is already subtracted from the spoil timer. In case of steel (and others), the resulting hot version comes almost spoiled out of the furnace. People didn't like it and this was the only available workaround. You can argue for both variants and this is now how it is until Wube fixes the bug.

ah understandable, i guess i never noticed that behaviour with DLC crafting being so fast that it comes out almost untouched regardless.