Fix WordPress Registration Error

Every time I try to register a new user on my WordPress site the form flashes “The email address is already in use,” yet the account still gets created. Clearly something in the workflow is mis-firing: the check for duplicate email runs, throws the error, but the user record is written anyway.

Here is what I know:
• User accounts are handled through WooCommerce together with the “Login & Register Customizer” plugin.
• I definitely rely on those two plugins; there may be others in the stack, but I’m unsure whether any recent updates could have triggered this problem.
• The error shows up consistently on every fresh signup, so it’s fully reproducible.

What I need from you:
1. Trace the source of the false-positive “email already in use” message.
2. Apply (or advise on) the cleanest fix—whether that’s a snippet, a filter, or a setting change—so the error appears only when the email truly exists.
3. Make sure the solution survives routine plugin and core updates.

Please be comfortable working inside WooCommerce, Login & Register Customizer, and standard WordPress hooks. Let me know how you plan to tackle the diagnosis, any access you’ll need, and roughly how long the repair should take.