As of #11466 we no longer have any logic to prevent a user from opening a wallet twice in two instances simultaneously. Not only could this break BDB (without the -privdb=false option, which I have really no idea why we even have a tuneable option for that), but we certainly don't have logic to handle such a case gracefully. It was noted in the original PR's description, but somehow was never followed up on before merge.
{
    InterruptHTTPServer();
    InterruptHTTPRPC();
    InterruptRPC();
    InterruptREST();
    InterruptTorControl();
    if (g_connman)
        g_connman->Interrupt();
    threadGroup.interrupt_all();
}
void Shutdown()
{
    LogPrintf("%s: In progress...\n", __func__);
    static CCriticalSection cs_Shutdown;
    TRY_LOCK(cs_Shutdown, lockShutdown);
    if (!lockShutdown)
        return;