How to reproduce:

• open Qt Creator 3.6.1 (comes with Qt 5.6.0 RC)
• load virtual keyboard example (Examples\QtVirtualKeyboard\quick\enterprise\virtualkeyboard\virtualkeyboard)
• place a breakpoint in VirtualKeyboard.qml:75 (passwordField, inputMethodHints binding)
• start debugging

Result:

Program: E:\Qt\5.6.0\5.6\msvc2013_64\bin\Qt5Cored.dll
Module: 5.6.0
File: qml\qqmlnotifier.cpp
Line: 123

QQmlEngine: Illegal attempt to connect to QQuickAnchors(0x29e021d7c20) that is in a different thread than the QML engine QQmlEngine(0x29e7d8fe350.