Converting from 4.4 to 4.6 - Crash at Level Loading

Hi there,
We have a map which works just fine in a 4.4 created project. we are trying to open the project inside 4.6.
Convert in place or convert a copy didn’t work because when we try to open that map loading crashes. Here is the Crash Info
we tried these steps with no result:

1-creating a basic code project in 4.6

2-copying C++ files from project to this recently created project
3-Adjusting and modifying code to follow new 4.6 coding instructions
4-Project compiles fine and editor opens the simple level with no problem
5-Copying Content folder from the project to the newly created project
6-Project opens and loads simple map with no problem

7- we tried to open the map but we encounter the same crash as mentioned above.