Persistent Checkout Form Error with WCAIO (403 on update_order_review)

Hello Support Team,

I am experiencing a persistent issue with the WooCommerce Cart All in One (WCAIO) plugin on my site new.ketoreal.shop.

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The Issue
• When using the floating cart checkout, I frequently get the error:
“Can not get form checkout, please reload page to try again.”
• AJAX logs show that the checkout form is returned correctly from /?wc-ajax=viwcaio_get_checkout_form, but the process fails on the next step.
• Specifically, the call to /?wc-ajax=update_order_review returns a 403 Forbidden error, which causes the checkout to break or loop.
• This happens on the first order stage (first time opening checkout from the cart).
• If the page is refreshed manually, checkout works normally afterwards.

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Steps Already Tested
• Disabled Cloudflare and checked firewall logs (no blocked requests).
• Disabled all caching and security plugins (no change).
• Switched from Elementor Pro Checkout widget → native WooCommerce Checkout (no change).
• Even with only WooCommerce WCAIO active and Storefront theme → issue persists.

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Debug Evidence

Example log extract:
ajaxSend → /?wc-ajax=viwcaio_get_checkout_form
ajaxComplete ← 200 /?wc-ajax=viwcaio_get_checkout_form

ajaxSend → /?wc-ajax=update_order_review
ajaxError × 403 – /?wc-ajax=update_order_review
ajaxComplete ← 403 /?wc-ajax=update_order_review

The checkout form HTML includes nonces and hidden fields (security, woocommerce-process-checkout-nonce, etc.), but update_order_review still fails with a 403 response until the page is reloaded.

Notes
• We do have some custom plugins on the site that cannot be fully deactivated, but we are also testing this issue in a separate staging environment to isolate the problem.
• The problem happens regardless of custom plugins being active or not.
• This bug is blocking live sales, as customers cannot place their first order without refreshing.

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Request

Could you please advise:
1. Is this a known bug with the current version of WCAIO?
2. Is there a compatibility issue with Elementor or WooCommerce core?
3. Is there a fix or patch available to make update_order_review work correctly from the floating cart without needing a full refresh?

This issue has been persistent despite multiple troubleshooting attempts on our side. Any help would be greatly appreciated.

Thank you,
Matthieu