It looks like we have figured out what is causing the issues of cooking your mods failing in 4.24.

If you can open the SDK, and you can edit your mod files, but you cannot cook it due to an unknown build error, or due to 'an item with the same key already exists', this is the fix for you:

1) Open the source files for your mod by right-clicking the plugin content folder, and selecting 'open in explorer'.

2) It should take you to a location that looks something like this [cdn.discordapp.com].
Make sure there is only one .uplugin file. The uplugin name is the same as the mod name.

3) Navigate up until you are inside the Mods folder, and check all the other mods. If any mod has a second .uplugin file, it will fail to cook your mod.

4) Repeat for the Plugins folder.