Random numbers to determine height of skiplist nodes consistently produce a height of one for all nodes

I am trying to create a SkipList, which utilizes random numbers to determine height. My implementation has a flaw, where the following often results in over 20 elements consistently failing to have a local_height above 1.

    local_height = 1;
    unsigned seed = std::chrono::system_clock::now().time_since_epoch().count();
    std::minstd_rand0 randGen(seed);
    int check = randGen() % 100;
    while(check < probOutOf100 && (local_height <= height || local_height <= 4)){                   
        local_height++;
        check = randGen() % 100;
    }

It seems that I can fix this through a workaround, but I'm worried that this will make my implementation slower.

    local_height = 0;
    unsigned seed = std::chrono::system_clock::now().time_since_epoch().count();
    std::minstd_rand0 randGen(seed);
    int successfulProb = -1;
    int randomBound = 500;
    while((successfulProb > (randomBound / 2) || successfulProb == -1) && (local_height <= height || local_height <= 4)){
        successfulProb = 0;
        for(int i = 0; i < randomBound; ++i){
            if(randGen() % 100 < probOutOf100) successfulProb++;
        }
        local_height++;
    }

Any ideas on what could be causing this bug or how to fix it? I can provide more of my code if needed. It seems that if I check the random numbers, it works consistently. Perhaps this is due to optimization?