i have spoken too soon. i had my dev environment in php 8.0 which was generating another error. this is NOT a confirmed bug.
i have confirmed that changing the config value:
Payment-Block Action on Shipping Change
Key: CHECKOUT_ONE_PAYMENT_BLOCK_ACTION
to refresh solves the issue.
TitanOwl you are correct.
Balaji, your problem is now solved.
best.
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