Fix Amelia Booking Restriction Bug (Not a trial project)

I’m running the latest release of the Amelia booking plugin on our WordPress site and, until recently, students could freely schedule multiple lessons without needing an account. Suddenly a new barrier appeared: after a student books one class, Amelia now blocks any further checkout attempts with the message that the email is already registered under a different username and asks them to log in—yet we have never offered, nor do we want to introduce, student log-ins.

Nothing in the setup has been changed and we rely solely on Amelia—no custom snippets, no other booking add-ons. I need someone who knows Amelia’s settings, short-codes and underlying PHP/SQL logic well enough to track down and eliminate whatever rule or hook is forcing this “one-time-only” limitation.

Your task
• Identify the root cause of the duplicate-email/login prompt.
• Re-enable unlimited bookings for the same email address without requiring an account.
• Confirm the fix works for several test students and survives a plugin update.

You’ll have WordPress admin access and, if necessary, temporary FTP/database credentials. A concise summary of what you changed and why completes the job.