Steps to reproduce:
1. Open attached project "866141.zip"
2. Build "TestScene" for Windows Store Universal 10 SDK
3. Open built VS solution
4. Deploy on local machine with x86/x64 Debug configuration
5. Press "Hide" button

Expected result: UI Panel is hidden
Actual result: Player crashes with Assertion failed: vector subscript out of range

Notes:
Isn't reproducible with Release/Master configuration
Is reproducible with .NET backend as well as il2cpp
Not reproducible on Editor/Windows Standalone

(Full output attached "output.txt")

Reproducible with: 5.5.0b1, 5.5.0p3, 5.6.0b3

Callstack:

ucrtbased.dll!_invoke_watson(const wchar_t * expression, const wchar_t * function_name, const wchar_t * file_name, unsigned int line_number, unsigned __int64 reserved) Line 224 C++
ucrtbased.dll!_invalid_parameter(const wchar_t * expression, const wchar_t * function_name, const wchar_t * file_name, unsigned int line_number, unsigned __int64 reserved) Line 113 C++
UnityPlayer.dll!00007fff381ac4c5() Unknown
UnityPlayer.dll!00007fff3848a191() Unknown
UnityPlayer.dll!00007fff3848b2de() Unknown
UnityPlayer.dll!00007fff381d2641() Unknown
UnityPlayer.dll!00007fff3a696030() Unknown
UnityEngineDelegates.dll!00007fff34ecc22d() Unknown
[External Code]