Why is std::filesystem::copy() throwing a "generic: 2" error?

Question

I've written a basic function which uses the std::filesystem to just copy all contents in a directory recursively to another directory. The code worked at first, but now broke out of nowhere and throws the following error when executing:

generic:2

My code:

#include <filesystem>
#include <string>
#include <iostream>

namespace fs = std::filesystem;

class backup {
private:
    fs::path location;

public:
    backup(std::string location_str) {
        location = fs::path(location_str);
    }
    
    std::error_code fetch_files(std::string src_str) {
        std::error_code err;
        
        fs::path src(src_str);
        fs::copy_options copy_opts = fs::copy_options::recursive | fs::copy_options::overwrite_existing | fs::copy_options::copy_symlinks;
        fs::copy(src, location, copy_opts, err);
    
        return err;
    }
    
int main(int argc, char* argv[]) {
    backup example_backup("~/Desktop/backup_destination");
    std::cout << backup.fetch_files("~/Desktop/backup_source") << std::endl;
    return 0;
}