Detection and removal of the cause of the game server crash

Hello, I have a game engine written in 2012, mostly in C++ with lua elements. I am unable to reproduce the bug that causes the engine to crash. The backtrace is quite unusual and reaches beyond my knowledge. I have a test VPS with identical environment and libraries as on production. I am asking a knowledgeable person to help me find the cause of this problem. In the case of error one, I only know as if somewhere the std::string constructor received an empty text, null. If you have any questions, I will be happy to answer and speed up the process. Source and all necessary things I will send after accepting the order.