Zend certified PHP/Magento developer

Error after checkout in Magento 2.4.5 after switching to PHP 8.1 “Something went wrong with your reuqest”

we have updated Magento from 2.4.4 to Magento 2.4.5 on our staging instance.

Now after switching to PHP 8.1 during checkout we get the error message “Something went wrong with your request”.

When switching back to PHP 7.4 all works well. The error logs do not show anything related. Does anyone possibly have an idea where to look for a fix?

We switched already to Luma Theme but no sucess.

Best regards