as the title suggests my redstone contraption for smelting things efficiently simply stopped working properly just a few minutes ago. I am using the first design of Mumbo Jumbo's video here but with eight furnaces. With eight furnaces one furnace always got skipped but luckily someone in the comment section said that changing the delay of the upper repeater (for the materials, not the fuel) to two ticks instead of one fixes it. I also needed a third row of hoppers on both sides so that every item can get smelted without getting stuck.
It absolutely did that and since then I am using the system a lot. Now just one hour ago it stopped working correctly and now it skips the seventh furnace (starting from the output chest it would be the second furnace), but only on the fuel side. Basically it distributes all items evenly, but not the fuel. The fuel side behaves as if the seventh furnace does not exist so it distributes all my coal evenly for seven furnaces.
I still have a creative version of the same world (from roughly one day ago) and when I put the same items in there it works perfectly, but if I rebuild exactly the same contraption (even in the same world), it skips one furnace. How can it be that it works all the time but just after a couple of days it does not work anymore? I did not update my game or anything (I did change shaders though but that can hardly be it).
I do not know if providing images will be helpful since both version look exactly the same, but if it is helpful I will destroy the decoration around it so that you can see the actual redstone parts.
On another hand, if it cannot be fixed, is there some other automatic smelting system that does not need a lot of space? There are a couple of 20+ furnace versions but I do not need that many and I don't want to use that much space for it either.
There is a locational hopper bug that sometimes skips or delays when items go through hoppers. If you watch a hopper as you stream a stack through, it should be showing an item constantly in it. not flashing an item. This is a bug that was fixed in 1.11 but can show up in servers especially if Spigot is installed. If you want reliability in how the items distribute, use minecarts.
Ilmango did a video on a this and a furnace array that you should see.