Google Ads traffic healthy but 2 of 7 branches saw website bookings drop from 7 to 1. What would you check?

Hello, I am in-house marketing with +1 year experience in managing google ads. I am managing Google Ads for a multi-branch medical clinic (knee treatment). I need help and advice in diagnosing sales drop because the insights looks fine but actual bookings at specific branches have crashed.

Our Diagnosis (last 14 days vs previous 14 days):

• Google Ads CTR: improving (8.6% → 9.6%)
• CPC: stable
• Impression share: improving (40% → 42%)
• Quality scores: no change
• GA4 direct conversions: only dropped 3.6%
• WhatsApp button clicks on landing page: only dropped 8.9%

The Issue

• Overall clinic sales/revenue for this service line is dropping.
• 2 out of 7 clinic branches saw direct website bookings (through our booking plugin) drop from 7 to 1 in the same period
• Other 5 branches are holding steady
• The landing page is shared across all channels (Google Ads, Meta, organic) — not branch-specific
• The gap between "people clicking WhatsApp" (barely dropped) and "people actually booking" (crashed) is massive
• Sales revenue declining even though traffic volume is the same

What we DON'T have visibility on:

• We can't track what happens after someone clicks the WhatsApp button. The journey is: ad click → landing page → WhatsApp button click → conversation with clinic staff → booking (or not). We lose visibility at the WhatsApp click.
• We don't know if those 2 branches are getting fewer WhatsApp inquiries, or the same inquiries but staff aren't converting them into bookings
• We can't attribute walk-in patients back to which marketing channel brought them

For anyone managing lead gen for clinics, dental, or local services — when your ad metrics look fine but bookings drop at specific locations, what was usually the cause? What should I be checking?

Is there any frameworks or checklists for diagnosing this?

Thank you in advance!