Can't install Unreal Engine 4.6.1 on OS X Yosemite

I recently subscribed to the Unreal Engine and tried to install Unreal Engine 4.6.1 using the Unreal Engine Launcher on OS X Yosemite.

It’s always the same: I click on Add Engine, choose 4.6.1, the download starts and then after ~20-30% the Unreal Engine Launcher becomes unavailable and I have to force quit it to start over.

I tried to restart my Mac, I tried to restart the Unreal Engine Launcher and I removed it completely (including caches and logs) and reinstalled it, but no luck.

In the logs there’s always this error:

[2015.01.03-22.13.44:510][  0]LogJson:Error: Json Value of type 'Null' used as a 'Object'.
[2015.01.03-22.13.44:512][  0]LogJson:Error: Json Value of type 'Null' used as a 'Object'.
[2015.01.03-22.13.44:516][  0]LogJson:Error: Json Value of type 'Null' used as a 'Object'.
[2015.01.03-22.13.50:167][  0]LogMac: === Critical error: ===
SIGSEGV: invalid attempt to access memory at address 0x0

[2015.01.03-22.13.50:168][  0]LogMac: _ZN17FSlateApplication21ProcessMouseMoveEventER13FPointerEvent Address = 0x9902295  (filename not found) [in UnrealEngineLauncher-Mac-Shipping]
_ZN17FSlateApplication19SynthesizeMouseMoveEv Address = 0x9902138  (filename not found) [in UnrealEngineLauncher-Mac-Shipping]
_ZN17FSlateApplication4TickEv Address = 0x98f6c7b  (filename not found) [in UnrealEngineLauncher-Mac-Shipping]
_ZN12FApplication3RunEv Address = 0x941fe61  (filename not found) [in UnrealEngineLauncher-Mac-Shipping]
_Z24UnrealEngineLauncherMainRK10TSharedRefI12FApplicationLN7ESPMode4TypeE0EE Address = 0x94223a3  (filename not found) [in UnrealEngineLauncher-Mac-Shipping]
_Z14RunApplicationv Address = 0x94224b2  (filename not found) [in UnrealEngineLauncher-Mac-Shipping]
-[UE4AppDelegate runGameThread:] Address = 0x9422b12  (filename not found) [in UnrealEngineLauncher-Mac-Shipping]
-[FCocoaGameThread main] Address = 0x94b99e6  (filename not found) [in UnrealEngineLauncher-Mac-Shipping]
__NSThread__main__ Address = 0x85666b7a (filename not found) [in Foundation]
_pthread_body Address = 0x8a4e22fc (filename not found) [in libsystem_pthread.dylib]
_pthread_body Address = 0x8a4e2279 (filename not found) [in libsystem_pthread.dylib]
thread_start Address = 0x8a4e04b1 (filename not found) [in libsystem_pthread.dylib]

If I don’t move the mouse over the window the Unreal Engine 4.6.1 will download and install as expected. The log shows there must be a bug with the mouse moving event.

_ZN17FSlateApplication21ProcessMouseMoveEventER13FPointerEvent