C++ map find return garbage value

my map is as follow: std::map<int, int> BuffList = std::map<int, int>(); it's being used multiple times by multiple threads (insert,remove,find,count) are the main functions.

When I test it by myself it works fine, but when its used by multiple people multiple times, the find function seems to return garbage values.

I also use critical section for the multithread handling.

Insert:

if (!buffCrit.IsLocked()) {
        buffCrit.Enter();
        BuffList[(PID + 4000000000 + (BuffID * 1000000))] = Value;
        buffCrit.Leave();
    }

Find

if (!buffCrit.IsLocked()) {
        buffCrit.Enter();

        if (BuffList.count((PID + 4000000000 + (BuffID * 1000000))))
            Value = BuffList.find((PID + 4000000000 + (BuffID * 1000000)))->second;

        buffCrit.Leave();
    }

Any suggestion?