I don't know what specifically is causing the error. It is happening when I'm running around land filling everything.

74.626 Error MainLoop.cpp:1207: Exception at tick 34467701: The mod Placeables: Show everything you can build with! (0.9.9) caused a non-recoverable >error.
Please report this error to the mod author.

Error while running event Placeables::on_player_built_tile (ID 45)
Placeables/control.lua:274: attempt to index local 'button' (a nil value)
stack traceback:
Placeables/control.lua:274: in function <Placeables/control.lua:257>

I'll update after I do some testing.

Okay figured it out I think. It happens when I either finish the stack in my hand or when I go into my inventory and try to use a random stack of landfill. Also in the placeables's box the landfill is being shown as the wrong item. As 201 rail chain signals. Which I believe I used to have but took them out to start land filling stuff. Now I only have one other item in my inventory other than landfill and its not signals and I have a bunch more landfill than 201. When I click on the rail chain signals in placeables the error also happens.

I went and put the rail chain signals back into my inventory. Now I have two railchain signals in my inventory but landfill is back. The other item (waterfill of the waterfill mod) is now turned into the signals. If I had more items they either get turned into a signal and bump the other item out (I've only ever seen two stacks of signals) or the item just doesn't show up.

And now with the rail chain signals in my inventory I can use either of the signal's listings in placeables to pick up the signals.

So seems like placeables item indexing/tracking somehow got messed up.

Yeah 0.9.9 brought some issues it seems. Downgrading to version 0.9.7 should fix those issues. Do you have discord/steam btw? Would be great to coordinate in more detail as I try to fix all of this

I believe I have fixed the issues! Well the crashing issues at least... not sure about the wrong buttons...

If you had just updated to 0.9.10 update to 0.9.12 i found another landfil-related crash and patched it

I do have steam. https://steamcommunity.com/profiles/76561198076262069/

Found another error! Something is funky with the sorting. Through taking stuff in and out of my inventory. I was able to get items to appear at the end where they shouldn't be. And when I take an item out of my inventory it is not removed from the list until I pick up/remove another item. The error below happened when I tried to pick up an item that was no longer in my inventory (I wanted to see if it was just the wrong icon like last time).

315.105 Error MainLoop.cpp:1207: Exception at tick 34995708: The mod Placeables: Show everything you can build with! (0.9.12) caused a non->recoverable error.
Please report this error to the mod author.

Error while running event Placeables::on_gui_click (ID 1)
Placeables/control.lua:382: attempt to index field '?' (a nil value)
stack traceback:
Placeables/control.lua:382: in function <Placeables/control.lua:374>

You know finding bugs in other peoples programs is a lot more fun than finding them in your own.

I sent a request, the name is a bit different though.
That is weird that its showing the wrong items to you. It may take some time to even figure out why, as its working fine on my end :(