Blender to Unity: mesh disappears when updating blend file https://imgur.com/MQOSdQm

I have this model in Unity and I'm trying to update it.

https://imgur.com/81iBr5J

I've only added some little planes on top of it (the road arrows), yet when I update in Unity (copy-paste blend file in Unity folder) the ground is gone and only the blocks and other items are present

https://imgur.com/WyksWIV

Would anyone know a fix to this? Thanks!
It looks like the original name of that mesh was changed at data level (3 vertex triangle tab on properties name is differenr than tab where cube is) on Blender.
Second reason, could be because the prefab is searching for a different hierarchy order. Thus, it breaks it (un parents it because of bone name or mesh name at data level).

BFCT_Schiller