react-hook-form: Uncaught TypeError: Cannot delete property '3' of [object Array]

I’m getting an error Uncaught TypeError: Cannot delete property '3' of [object Array].

My component is a dynamic that uses useFieldArray({ name: 'step.answers', control }).

    if (defaultValues && fields.length < defaultValues.length) {
      defaultValues.pop(); // here where it breaks
      set(fieldArrayDefaultValuesRef.current, name, defaultValues);
    }

defaultValues.length is 4, fields.length is 2. That’s why defaultValues.pop(); is fired.

Could you clarify please, why this error might happen? I can debug further then.

It would be nice to have a clarification error in the console for such cases.

I’d be glad to create a codesandbox, but my form is very complicated. With funnel and little-state-machine.