Need PHP Expert to fix and optimice a function

Need to optimice and fix a php function. The issues are logged and identified by a .log file. The main issue its that sometimes the function process and mix the requests and it does a slow/bad/freezes on frontend due to these issue on the function logic. The function process many requests per second, normally (in log) it start and ends a request them start next, but sometimes it start to process 1 and while processing start another, so data got crazy and its displayed on frontend as freezes. The function its little but very important. I need it solved today, is some hours as much. I will give you the file wich contain the function and the log file with the issues, to test it i will upload it and check it logging.