The following API test has been asserting on macOS and iOS debug bots since https://commits.webkit.org/247985@main landed:

    TestWebKitAPI.PushAPI.firePushEventWithNoPagesTimeout
        ASSERTION FAILED: m_connection
        /Volumes/Data/worker/bigsur-debug/build/Source/WebKit/UIProcess/AuxiliaryProcessProxy.h(80) : IPC::Connection *WebKit::AuxiliaryProcessProxy::connection() const
        1   0x10799df89 WTFCrash
        2   0x110816f7b WTFCrashWithInfo(int, char const*, char const*, int)
        3   0x111966cc9 WebKit::AuxiliaryProcessProxy::connection() const
        4   0x112680fdb WebKit::NetworkProcessProxy::terminate()
        5   0x112784a65 WebKit::WebsiteDataStore::terminateNetworkProcess()
        6   0x111a1588a -[WKWebsiteDataStore(WKPrivate) _terminateNetworkProcess]
        7   0x100b4c2ff terminateNetworkProcessWhileRegistrationIsStored(WKWebViewConfiguration*)
        8   0x100b4e183 PushAPI_firePushEventWithNoPagesTimeout_Test::TestBody()
        9   0x1010df674 void testing::internal::HandleSehExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*)
        10  0x1010a230b void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*)
        11  0x1010a2243 testing::Test::Run()
        12  0x1010a3414 testing::TestInfo::Run()
        13  0x1010a4555 testing::TestSuite::Run()
        14  0x1010b35dd testing::internal::UnitTestImpl::RunAllTests()
        15  0x1010e4a34 bool testing::internal::HandleSehExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*)
        16  0x1010b2f7b bool testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*)
        17  0x1010b2e4d testing::UnitTest::Run()
        18  0x1007e13b1 RUN_ALL_TESTS()
        19  0x1007e1342 TestWebKitAPI::TestsController::run(int, char**)
        20  0x10106cf7f main
        21  0x7fff203e4f3d start
        22  0x2

https://results.webkit.org/?suite=api-tests&test=TestWebKitAPI.PushAPI.firePushEventWithNoPagesTimeout