Why is Shop Pay or express checkout behaving strangely?

Shop Pay or express checkout (Apple Pay, Google Pay, PayPal express) glitches when customer accounts aren’t configured correctly, the express button conflicts with a theme cart drawer, discounts/shipping don’t carry through the accelerated flow, or a checkout customization clashes with the wallet. We test the full accelerated path on a preview store, isolate the clashing setting or script, and make the express flow match your standard checkout.