Cannot increment returned sregex_iterator?

I'm trying to construct an sregex_iterator from some complicated computations so I wrote a function to do this and return the iterator. However when I then want to increment the returned iterator, the program crashes, sometimes throwing std::bad_alloc, sometimes not..

I managed to reduce it to a MWE with little code but somehow I still cannot figure out what is happening..

#include <iostream>
#include <regex>

using namespace std;

sregex_iterator get_it(const string& str) {
    regex r("([ab]{3})");

    auto it = sregex_iterator(str.begin(), str.end(), r);
    cout << (it == sregex_iterator() ? "end\n" : "more\n");
    ++it; //works as expected .. no crash. When commented out, program still crashes
    cout << "can incr ..\n";

    return it;
}

int main(int argc, char** argv) {
    auto it = get_it("aaa bbb");
    cout << (it == sregex_iterator() ? "end\n" : "more\n");
    ++it; //this crashes the program

    cout << "success\n"; // never runs
}

To compile I use g++ (Ubuntu 7.4.0-1ubuntu1~18.04.1) 7.4.0 with -std=c++11 flag.

This runs and outputs

more
can incr ..
more
terminate called after throwing an instance of 'std::bad_alloc'
  what():  std::bad_alloc

So increment works in the function where I construct the iterator, but not outside. But all that happens is copy (/move if RVO happens) of the iterator, which should not invalidate it? Surely the sregex_iterator does not store reference or pointer to any of its constructed-from arguments?

My only guess is there must be a ref/ptr to temporary somewhere but I do not see it.. or what am I missing here?