Getting "This value should not be null" when using IEF

Hi,
first of all, I am not sure if this is an IEF module problem or not so I decided to post here since someone might point me in the right direction.
I have IEF version 1.0.0-rc7 installed with Allow select widget for "Add existing items" ✨ Allow select widget for "Add existing items" Needs work patch applied and 1.1.0 version of Commerce Checkout Order Fields.

Problem/Motivation

1. I have created 2 new user profiles called Pickup/Delivery Address which hold information about users addresses and both have "Profiles of this type represent Commerce customer profiles" checkboxes checked.
2. I have created 2 new required entity reference fields on my order type which use a view to return correct results based on current user.
3. For my field widget I used IEF - Complex that allows the user to select existing addresses already created in the address book, or create a new one in the checkout process.
4. When user creates a new profile or re-uses the existing profile, no AJAX or watchdog errors occur, but when user tries to proceed to "Review" step of the checkout flow "This value should not be null" error occurs and checkout process stays on the same step.
5. What I found out:

• When new profile is created during the checkout, it does not appear in the address book
• When new profile is edited during the checkout, changes do not reflect in the address book
• When using autocomplete or select widgets for these fields it works as expected

Steps to reproduce

• Create new entity reference field on your order type
• Use Inline Entity Form - Complex or Simple on manage form display
• Try create new or use existing value of the referenced entity

Thanks for your help!