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.
/**
 * .. and a wrapper that just calls func once
 */
template <typename Callable> void TraceThread(const char* name,  Callable func)
{
    std::string s = strprintf("bitcoin-%s", name);
    RenameThread(s.c_str());
    try
    {
        LogPrintf("%s thread start\n", name);
        func();
        LogPrintf("%s thread exit\n", name);
    }
    catch (const boost::thread_interrupted&)
    {
        LogPrintf("%s thread interrupt\n", name);
        throw;
    }
    catch (const std::exception& e) {
        PrintExceptionContinue(&e, name);
        throw;
    }
    catch (...) {
        PrintExceptionContinue(nullptr, name);
        throw;
    }
}
std::string CopyrightHolders(const std::string& strPrefix);
template <typename T, typename... Args>
std::unique_ptr<T> MakeUnique(Args&&... args)