Materials/Textures only appear in squares/crash fix?

I’m currently trying to create my landscape and UE4 cannot seem to allow me to paint materials/textures into the environment unless they appear as perfect squares. I’ve tried rebuilding all of the lighting at production quality and when I try to paint it crashes the entire Engine. I also tried to repaint some portions of another map I was working on and it wouldn’t let me at all. Everything would turn grey/black and only the areas I painted (which were still massive squares) would have texture. Oh, and if I tried to use another texture, the engine would crash. Here is a Gif of the Squares. A few seconds after it, the entire engine crashed and gave me the error listed below. Also, crashes only seem to occur when using the paint tool for foliage, textures, shader’s and materials.

GIF:

84366-7122a894a757da530901460b4b5883bf.gif

Crash Error:

Unknown exception - code 00000001 (first/second chance not available)

"Assertion failed: !Value || Value->IsValidLowLevel() [File:D:\BuildFarm\buildmachine_++depot+UE4-Releases+4.10\Engine\Source\Runtime\Engine\Private\Ma

UE4Editor_Core!FDebug::AssertFailed() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\core\private\misc\outputdevice.cpp:374]
UE4Editor_Engine!FUniformExpressionSet::CreateUniformBuffer() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\engine\private\materials\materialuniformexpressions.cpp:354]
UE4Editor_Engine!FMaterialRenderProxy::EvaluateUniformExpressions() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\engine\private\materials\materialshared.cpp:1594]
UE4Editor_Engine!<lambda_750448c5cd9789c3d5618b9eb116be51>::operator()() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\engine\private\materials\materialshared.cpp:1626]
UE4Editor_Engine!FMaterialRenderProxy::CacheUniformExpressions() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\engine\private\materials\materialshared.cpp:1610]
UE4Editor_Engine!TGraphTask<`FMaterialRenderProxy::CacheUniformExpressions_GameThread'::`5'::EURCMacro_FCacheUniformExpressionsCommand>::ExecuteTask() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\core\public\async\taskgraphinterfaces.h:779]
UE4Editor_Core!FTaskThread::ProcessTasks() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\core\private\async\taskgraph.cpp:539]
UE4Editor_Core!FTaskThread::ProcessTasksUntilQuit() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\core\private\async\taskgraph.cpp:340]
UE4Editor_RenderCore!RenderingThreadMain() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\rendercore\private\renderingthread.cpp:310]
UE4Editor_RenderCore!FRenderingThread::Run() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\rendercore\private\renderingthread.cpp:411]
UE4Editor_Core!FRunnableThreadWin::Run() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\core\private\windows\windowsrunnablethread.cpp:74]