Everytime this test fails (actually it does at least when elapsedTime = 0) the engine stucks in an infinite loop if the backend uses calls to g_system methods to call the timer handler.
Moving the call to delayMillis outside the test block solves the issue (provided that the backend uses delayMillis to call the timer handler), as elapsedTime can progress whether interpolated tempPalette is already equal to _currentPalette or not.