Got this with the new update.

The mod Tier Generator (0.4.0) caused a non-recoverable error. Please report this error to the mod author.
Error while running event tier-generator::on_configuration_changed gui-modules/gui.lua:189: attempt to index upvalue
'namespace_metadata' (a nil value)
stack traceback:
gui-modules/gui.lua:189: in function 'setup'
gui-modules/gui.lua:343: in function 'on_configuration_changed"
core/lualib/event_handler.lua:87: in function
_core__/lualib/event_handler.lua:84>

I don't really know the situation that causes that, but I do now remember the event handler itself handles it.
So I've gone ahead and added the same check to gui-modules, and updated Tier Generator to use that new version.

Thanks for reporting this!
I spent 5 days entirely rewriting the UI just so I didn't hate myself when working on it, and so I kind of rushed it out to be done with it for a while.

I get what you mean, gui-s have never been my forte so I just try to avoid making them at all costs.
The first error happened on loading into a game.

I am now getting this error right after loading into the game.

The mod Tier Generator (0.4.1) caused a non-recoverable error. Please report this error to the mod author.
Error while running event tier-generator::on_nth_tick(1) LuaGuiElement API call when LuaGuiElement was invalid.
stack traceback:
[C]: in function 'newindex'
_tier-generator/interface/tierMenu.lua:280: in function '?' _tier-generator__/library.lua:401: in function _tier-generator__/library.lua:391>

I tested the mod on its own and with my current mod set and it seems the crash doesn't happen on starting a new game but might instead be from loading into an active game that used the old version of the mod.

I have an idea for what is happening. But not why it's happening

The reference to the calculate button is invalid, but I don't know why it would be.
The library could think the UI definition changed, so it's wiping it and rebuilding it, but then it should also update the references in global.
If I were to just check its validity, I'm sure I'll have problems with it elsewhere as most of my code assumes the references are valid since they should be static.

Could you send me the save that has the problem? I might be able to recreate it myself, but, like I said, I'm too tapped out.

For now, disabling the mod, saving without it, and then loading it with the mod should work as a workaround.

I just tried disabling the mod, saving without it, and then loading it with the mod again but I still seem to get an error.

The mod Tier Generator (0.4.2) caused a non-recoverable error. Please report this error to the mod author.
Error while running event tier-generator::on_nth_tick(1) LuaGuiElement API call when LuaGuiElement was invalid.
stack traceback:
[C]: in function 'newindex'
__tier-generator/interface/tierMenu.lua:280: in function '?' _tier-generator__/library.lua:401: in function <tier-generator/library.lua:391>

How should I send you the save? I don't think it can be done through this site.

If you want, you can send it to me on discord: pennyjim

Either that, or upload it to a file sharing site and send the link here

And my latest update didn't fix it? I don't really know where the GUI could be getting invalidated..

I have been told that I should be checking the validity every single time I use them since any mod can always all GUIs. The library is already pretty safe about it, but in tier generator, I go about a few things unsafely. Even though the library should be making sure the references are either valid or the state is deleted, I might need to just add checking to my mod.

I'll need to test how it reacts to the "rug" (the entire UI) getting pulled out from under it.

I have sent you friend request. My username is Gentleman Rogue on Discord.