Payment systems broke after the update. Why is PS_INVOICE_ID not generated?

Question

1C-Bitrix

Good afternoon, colleagues! Again I turn to you for help and really hope for good advice.
After updating Bitrix from 03.02, payment systems broke down on the test site, or rather, the YuKassa widget with the response from the API - Wrong request. Incorrect interaction with YuKassa API.

After calling tech support and digging through the code, I found that the PS_INVOICE_ID parameter remains empty in the payment object, while on another test site (where everything works) this parameter is present at the same stage. Further formation of the request is already incorrect.

Tell me, please, where, how and where should this parameter be formed? I would be very grateful for your help!

Answer 1

The problem was that the master value of mbstring.func_overload = 2, because of this, the Content-Length header was incorrectly specified and the request to Yukassa was cut off. More details in the comments.
Logs for payment systems in Bitrix can be viewed in the b_sale_pay_system_err_log table. If you set the option via the console, debug level logs will be written

\Bitrix\Main\Config\Option::set('sale', 'pay_system_log_level', 0);