Hmm...

Are you using ProGuard in release but not in debug? That, combined with the fact that the input composable is wrapped in an if statement, might mean that compose "thinks" there's a view there (and reserves a bit of space).

Maybe instead of

if (isItemChecked) {
    CustomInputText()
}

try

AnimatedVisibility(visible = isItemChecked) {
    CustomInputText()
}

Hope this works!