v1.2.6: How to fix error when checkout "Something is wrong with your request, please try again later"?

QUESTION:

I install the module v1.2.6 (latest version) to my site Magento 2.4.3 CE, however, when we proceed checkout, it shows the message:  "Something is wrong with your request, please try again later"

Is there a fix available?

ANSWER: 

Please edit the file app/code/Bss/CheckoutCustomField/Model/Observer/SaveOrder.php as below to fix this module's error:

Or download the file attached below to override the current file on your site.

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