Hello Nox_A15,
From what you have described you are having an issue with losing your collision whenever you re import a Static Mesh into UE4.
I attempted to recreate the loss of collision inside of a test project.
These are the steps I took :
1.) Created a new project
2.) Created a cube inside of Maya
3.) Imported that object into the new project and made sure that Auto Generate Collision was turned on
4.) I added the box to my level
5.) I opened up the details of the mesh by double clicking it in the content browser. This was to make sure that I could see collision on my mesh.
6.) Played in editor. This was so that I could confirm that the collision was working.
7.) I then stopped the PIE session and went to the SM in the content browser.
8.) I right clicked the mesh and chose to reimport.
9.) I then built the level and played again.
I was not able to recreate the loss of collision that you are experiencing. If any of these steps are different from what you have done inside of your project then please let me know.
There are a few questions that I have for you
1.) Can you recreate this in another project or in the 4.9.4 preview?
2.) Does this happen on any other mesh inside of your project?
3.) If you would link me your DxDiag?
After you have determined if any of my steps differ from yours and tried the above mentioned troubleshoots then please let me know what you find out. I will continue to investigate this matter in the meantime.
Thank you,