When I run bitcoin-qt it does not properly start up and hangs in futex():

The last calls shown in strace are:
```
futex(0x7f3f7bfd77e4, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7f3f7d812c60, FUTEX_WAIT, 65792, NULL
```

gdb shows:

```
(gdb) bt
#0  syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
#1  0x00007ffff5e26d2f in __cxa_guard_acquire () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#2  0x00007ffff7e06dcc in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Network.so.5
#3  0x00007ffff7e0b706 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Network.so.5
#4  0x00007ffff7e2af21 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Network.so.5
#5  0x00007ffff7e32080 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Network.so.5
#6  0x00007ffff7df1c67 in QSslCertificate::QSslCertificate(QByteArray const&, QSsl::EncodingFormat) ()                                                                                        
   from /usr/lib/x86_64-linux-gnu/libQt5Network.so.5
#7  0x00007ffff7e07fe6 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Network.so.5
#8  0x00007ffff7dfb09d in QSslConfiguration::defaultConfiguration() () from /usr/lib/x86_64-linux-gnu/libQt5Network.so.5                                                                      
#9  0x000055555564841f in main () at qt/bitcoin.cpp:579
#10 0x00007ffff5a49b17 in __libc_start_main (main=0x555555648380 <main>, argc=1, argv=0x7fffffffdcc8, init=<optimized out>, fini=<optimized out>,                                             
    rtld_fini=<optimized out>, stack_end=0x7fffffffdcb8) at ../csu/libc-start.c:310
#11 0x0000555555657dca in _start () at /usr/include/c++/8/ext/new_allocator.h:116
```

I understand that this might also be a problem in Qt rather than bitcoin-qt.
But other Qt applications do not show this problem. So I'd be happy to get any hint to debug this further.

Thanks!

{
    Q_OBJECT
public:
    explicit BitcoinApplication(interfaces::Node& node, int &argc, char **argv);
    ~BitcoinApplication();
#ifdef ENABLE_WALLET
    
    void createPaymentServer();
#endif
    
    void parameterSetup();
    
    void createOptionsModel(bool resetSettings);
    
    void createWindow(const NetworkStyle *networkStyle);
    
    void createSplashScreen(const NetworkStyle *networkStyle);
    
    void requestInitialize();
    
    void requestShutdown();
    
    int getReturnValue() const { return returnValue; }