We are facing a weird issue where Magento throws 500 server error to very few customers. The error log says
PHP Fatal error: Allowed memory size of 2147483648 bytes exhausted (tried to allocate 96 bytes). Notice we already gave 2GB of memory_limit in PHP, so this is definitely not the memory issue but something else. We tried many ways to reproduce this without any luck. Once the customer gets this 500 error, s/he gets it all the time when they visit our website again.
What could be wrong? How to reproduce this kind of error?