ItemFlexer 1.1.1, Fabric 0.10.8
Crash Report: https://paste.ee/p/VGob0

That looks like you messed up the config file, make sure it's in a proper format

That's strange, that was the first time I launched the mod, so I didn't have the chance to modify the config.

Ah, I see. There's no default value for cooldown when the config file generates; setting it to 0 fixes this.

Strange, that shouldn't be possible

Yeah looking at microconfig's code that value should always be set, unless their some quirk of reflection or file writers I can't find easily

Is this consistent behavior? (Always happens when the config file is missing?)

Fixed in latest version