Packaging failed

Hi there,
Im completely new to using unreal4.
I have been working on a test game project and had several successful package tests before v4.20. I have messed with the camera setups and the actor (gamemode?), if thats right but Im not sure whats causing my current package to fail. (I have installed the requirement visual studio, dx kit) I also tried to delete the saved folder and intermediate but no success. I will post bellow some of what it seems to be the error, but being a beginner I dont understand what the problem means and how to fix it. Can you please help me if possible? Thank you in advance and apologies for my limited knowledge and if I confuse you. I cant find some solution online.

" UATHelper: Packaging (Windows (64-bit)): LogInit: Display: LogBlueprint: Error: [Compiler PersistentLevel.walksim] Couldn’t find object for bound event node OnActorBeginOverlap (None) from Source: /Game/walksim.walksim:PersistentLevel.walksim
UATHelper: Packaging (Windows (64-bit)): LogInit: Display: LogBlueprint: Warning: [Compiler PersistentLevel.walksim] OnActorBeginOverlap (None) is referencing an Actor that no longer exists. Attached logic will never execute.
UATHelper: Packaging (Windows (64-bit)): LogInit: Display: LogBlueprint: Warning: [Compiler PersistentLevel.walksim] [0014.05] Compile of PersistentLevel.walksim failed. 1 Fatal Issue(s) 1 Warning(s) [in 3 ms] (/Game/walksim.walksim:PersistentLevel.walksim)
UATHelper: Packaging (Windows (64-bit)): LogInit: Display: LogPhysics: Warning: PHYSX: (D:\Build++UE4+Release-4.20+PhysX_Compile\Sync\Engine\Source\ThirdParty\PhysX3\PhysX_3.4\Source\PhysXCooking\src\convex\QuickHullConvexHullLib.cpp 937) eINTERNAL_ERROR : QuickHullConvexHullLib::findSimplex: Simplex input points appers to be coplanar.
UATHelper: Packaging (Windows (64-bit)): LogInit: Display: LogPhysics: Warning: Failed to cook convex: /Game/CUSTOMASSETS/arcs/PROP_13.PROP_13 0 (FlipX:1). The remaining elements will not get cooked.
UATHelper: Packaging (Windows (64-bit)): LogInit: Display: LogPhysics: Warning: Attempt to build physics data for /Game/CUSTOMASSETS/arcs/PROP_13.PROP_13:BodySetup_0 when we are unable to.
UATHelper: Packaging (Windows (64-bit)): LogInit: Display: LogPhysics: Warning: PopulatePhysXGeometryAndTransform(Convex): ConvexElem is missing ConvexMesh
UATHelper: Packaging (Windows (64-bit)): LogInit: Display: LogPhysics: Warning: ForeachShape(Convex): [/Game/CUSTOMASSETS/arcs/PROP_13.PROP_13] ScaledElem[0] invalid
UATHelper: Packaging (Windows (64-bit)): LogInit: Display:
UATHelper: Packaging (Windows (64-bit)): LogInit: Display: Failure - 1 error(s), 24 warning(s)
UATHelper: Packaging (Windows (64-bit)): LogInit: Display:
UATHelper: Packaging (Windows (64-bit)):
UATHelper: Packaging (Windows (64-bit)): Execution of commandlet took: 77.75 seconds
UATHelper: Packaging (Windows (64-bit)): Took 85.2316837s to run UE4Editor-Cmd.exe, ExitCode=1
UATHelper: Packaging (Windows (64-bit)): ERROR: Cook failed.
UATHelper: Packaging (Windows (64-bit)): (see C:\Users\mlapp\AppData\Roaming\Unreal Engine\AutomationTool\Logs\D+UE_4.20\Log.txt for full exception trace)
UATHelper: Packaging (Windows (64-bit)): AutomationTool exiting with ExitCode=25 (Error_UnknownCookFailure)
UATHelper: Packaging (Windows (64-bit)): BUILD FAILED
PackagingResults: Error: Unknown Cook Failure
LogSlate: FSceneViewport::OnFocusLost() reason 0
LogSlate: Took 0.000280 seconds to synchronously load lazily loaded font ‘…/…/…/Engine/Content/Slate/Fonts/DroidSansMono.ttf’ (77K)"

Hi, did you find a solution for this?

Hi there! Thank you for your comment. While I was able to temporarily solve it there was other errors on builds. Can you please point me out some proper guide steps on how to build a project that has several maps to choose from? I appreciate your time and thank you in advance.