I found a couple of issues going on with my refinery, using the up-to-date version of this mod and game versions 0.15.9 through 0.15.12, which have made this less useful than it's been in the past.

The biggest thing is that it can't recycle a number of things that it used to be able to - an example is that it can't uncraft electronic circuits, or advanced circuits. Electric mining drills are also unrecyclable. To be specific, this is the "cannot be smelted" problem, not one of the machine clogging on something that uses multiple stacks of one ingredient.

I'm also not too thrilled at the loss of item overflow in the product slots, especially since I tend to just stick the recycling plant in an empty corner and use it manually, so setting up a whole output/storage thing is kinda a pain. That and I'll probably forget that I can't safely uncraft some stuff due to the "multiple stacks of one ingredient" thing that I know you're already aware of.

factorio changed smelting mechanics in 0.15 which prevents item overflow. It's base game issue, not the mod.

Hmm, that's interesting, I will have to test that circuit thing. Might I ask if you're using any "big" game-changing mods, like bobs, angels, 5dims, etc? Unless the base game changed the circuit crafting group, those should be uncraftable like any other item. I will test this tomorrow

I will also check whether I can fix the output multi-stack item issue as well. I should be able to check if stack size is greater than ingredient amount, and have it not make a recipe at all for those. It definitely is more noticeable of an issue now

Would it be possible to dynamically change the stack size when it tries to uncraft a dense item and then set it back when it's done? Maybe as a mod option?

Hmm, I'm thinking there's a distinct boundary between "preloading" and "in-game" that would prevent this from being possible. But I'm not 100% on that. Iirc, recipe stuff can only be modified from within the preloading stage, but I have seen certain mods skirt around this issue (like GDIW hotkey).

I'm currently doing fixes and updates for the next version, so now's a good time to test

That makes me wonder what would happen to the base, if something like concrete suddenly had their stack size increased. Any buffer chests containing concrete could suddenly hold more, so bots and inserters would try to put more concrete inside to fit the new stack size. But then that stack size would be shrunk.. yet the items have already been stacked higher than the chest can hold... could be dropped item issues or item deletion, neither of which are desirable...

So I decided against dynamically increasing the stack size, because of potential issues that could cause. Instead, I simply disabled the ability to recycle any item whose ingredient count exceeds its stack size. Easier this way.

As for the circuit uncrafting, perhaps check your output slots? I tried in vanilla (w/Creative Mode, but that shouldn't make a difference?) and circuits uncrafted just fine. Even with bobs electronics, it worked fine.

Not sure if this is the right place but i downloaded this mod recently running 0.16.51 and i noticed it won't recycle cargo trains. I found something else it won't recycle which is from another mod so i'm not expecting that to be resolved any time soon.

Vehicles and power armor are both currently unrecyclable. I could probably add a setting to allow that, but it wouldn't eject the modules/cargo, which would be destroyed in the process. You'd only get the materials back for the vehicle/power armor, not anything inside of it.

As for inter-mod compatibility, so long as it's not a vehicle or power armor, it should be recycable, even if it's from another mod. There might be some other categories I'm not remembering that also can't be recycled, but I know for sure those 2 cannot.

Not that it's important but i did also notice that the fusion reactors from https://mods.factorio.com/mod/Fusion-Reactor-Upgrade are not currently going through. Don't get me wrong, i'm not disappinted because i get it's from another mod. But guessing reactors are one of the non recyclable things, although battries are.

Ahh, right, any item that requires more than 1 stack of an item also can't be recycled in the current version. So those heavy recipes, like the vanilla Nuclear Reactor and Reactor Silo, can't be recycled, because the output slots can only take 1 stack of 1 item, and they don't spill over into the other slots (they used to, many versions ago...)

So if a recipe requires 1000 concrete, and the stack size is 200, when you recycle it, you get 200 concrete, not 1000. I have this disabled in the current version, but I could add that as a setting as well.