Asynchronous Image loading crashes

Hi, I am working on Project to present a lot of quite high Quality Images, on a Touch Screen using unreal, I am loading the files from the hard drive using async() with a future to fire an Event when the loading is finished. This is working for some time, and then randomly it chrashes.
Log Output:

2019.11.17-15.33.06:899][473]LogThreadingWindows: Error: Runnable thread TaskGraphThreadNP 0 crashed.
[2019.11.17-15.33.06:899][473]LogWindows: Error: === Critical error: ===
[2019.11.17-15.33.06:899][473]LogWindows: Error: 
[2019.11.17-15.33.06:899][473]LogWindows: Error: Fatal error!
[2019.11.17-15.33.06:899][473]LogWindows: Error: 
[2019.11.17-15.33.06:899][473]LogWindows: Error: Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0xffffffff
[2019.11.17-15.33.06:899][473]LogWindows: Error: 
[2019.11.17-15.33.06:899][473]LogWindows: Error: [Callstack] 0x00007ff76b5eac5c Puzzle.exe!<lambda_865e3fa39d6d77362f5f4e121c5c33cf>::operator()() [f:\puzzle_04_11\source\puzzle\imageloader.cpp:32]
[2019.11.17-15.33.06:899][473]LogWindows: Error: [Callstack] 0x00007ff76b30e470 Puzzle.exe!FFutureState::MarkComplete() []
[2019.11.17-15.33.06:899][473]LogWindows: Error: [Callstack] 0x00007ff76b5ebf7d Puzzle.exe!TGraphTask<TAsyncGraphTask<UTexture2D *> >::ExecuteTask() [d:\unreal\ue_4.23\engine\source\runtime\core\public\async\taskgraphinterfaces.h:847]
[2019.11.17-15.33.06:899][473]LogWindows: Error: [Callstack] 0x00007ff76b62a257 Puzzle.exe!FTaskThreadAnyThread::ProcessTasks() []
[2019.11.17-15.33.06:899][473]LogWindows: Error: [Callstack] 0x00007ff76b62b25d Puzzle.exe!FTaskThreadAnyThread::ProcessTasksUntilQuit() []
[2019.11.17-15.33.06:899][473]LogWindows: Error: [Callstack] 0x00007ff76b6322cb Puzzle.exe!FTaskThreadAnyThread::Run() []
[2019.11.17-15.33.06:899][473]LogWindows: Error: [Callstack] 0x00007ff76ba37a7f Puzzle.exe!FRunnableThreadWin::Run() []
[2019.11.17-15.33.06:899][473]LogWindows: Error: [Callstack] 0x00007ff76ba2d9e1 Puzzle.exe!FRunnableThreadWin::GuardedRun() []
[2019.11.17-15.33.06:899][473]LogWindows: Error: [Callstack] 0x00007fff77cf7bd4 KERNEL32.DLL!UnknownFunction []
[2019.11.17-15.33.06:899][473]LogWindows: Error: [Callstack] 0x00007fff78d8ced1 ntdll.dll!UnknownFunction []

I tried using the ThreadPool, Thread, and the TaskGraph and it all fails with the same error.

The Line in my ImageLoader where it Fails is the Future.GetValid() where it is supposed to wait for the finished Task.

Does anybody have an Idea what to do?

Thank you.