WordPress Registration Validation Fix

Users trying to sign up on my WordPress site see an “invalid ID” error and the form refuses to submit. I only need a straightforward fix: identify what’s triggering the validation, adjust the logic (most likely inside one of our custom plugins), and confirm that accounts can now be created without that error appearing.

Key points
• WordPress with several custom plugins active—no custom theme edits involved.
• Error reproduces every time a new user fills the form, even with simple alphanumeric IDs.
• No design changes required; just correct the validation and ensure the form completes normally.

Deliverable
A brief report of what you changed plus the code snippet, filter, or plugin patch you applied so I can re-apply it in staging or future updates.

I’m looking for someone who has fixed similar registration bugs before and can turn this around quickly today.