I have tried without overwriting it, but still no luck
While I haven't found the exact cause of it, I looked at the file and noticed that the GLTF file is exporting the vertices for every face that needs to be connected and as such the vertex count is going up a lot while the FBX just has the vertices connected normally,if you import the meshes and then select a face and move them and compare how it is for the two models you will understand what I mean