you can check it out here on UDN, https://udn.unrealengine.com/s/question/0D54z00008PS4rGCAT/invalid-mesh-data-from-tracked-geo
you need to modify the AppleARKitMeshData.cpp file
look for lines
line 180 InVertices.stride == sizeof(FVector) &&
and
line 229 InNormals.stride == sizeof(FVector) &&
replace those with:
line 180 InVertices.stride == sizeof(FVector3f) &&
and
line 229 InNormals.stride == sizeof(FVector3f) &&