Exporting models and animations from the game for use in Unreal Engine.

Hello everyone,

I am a representative of the Heroes 5: Reborn project. We are trying to recreate Heroes of Might and Magic 5 using the Unreal Engine.

You can see the initial results of our work here:

Currently, we are using Archangel and 3ds Max 2008 with plugins for SMD and GR2 files to export game models and animations.
Briefly, the process is as follows:
1) We load the model and apply textures to it in Archangel (for static models, we then simply export it to OBJ).
2) We load the GR2 skeleton into Archangel and export the model with the skeleton in SMD format.
3) We import the SMD model with the skeleton into 3ds Max 2008 using the SMD import plugin (by Wunderboy).
4) We import the GR2 animation into 3ds Max 2008 using the GR2 import plugin (NWN2Utils).
After this, we can export the animated model from 3ds Max in FBX format.

In most cases, this method works correctly. However, some models have problems at the stage of applying animation to the skeleton in 3ds Max.
This usually happens with models that have complex skeletons; for example, the animations for most mounted units do not work correctly.

We preliminarily believe that the problem is either in the SMD import plugin, which incorrectly imports the model's skeleton into 3ds Max, or in Archangel, which incorrectly applies the skeleton to the game model. This is because when importing a bare GR2 skeleton into 3ds Max and applying animations to it, we see that everything works as it should.
We have tried some other methods, such as using the SMD import plugin for Blender and using the Noesis program to convert GR2 animations to FBX/SMD formats, but this did not yield any results.

Therefore, we would like to ask for help from those who have experience working with game models and animations and may be able to suggest a more optimal and less error-prone method for exporting models. Or suggest a way to solve the problems that arise when working with Archangel and 3ds Max.

As an example of a problematic model, I have uploaded the files for the Order hero to Google Drive: https://drive.google.com/drive/u/2/folders/15eu2R0Dcn2N5ggIAZnkAfzmi0tuCV2-1
There are the original game model files (geom, gr2 skeleton, gr2 move animation), the SMD file from Archangel with the model and skeleton, and MAX and FBX files with the knight's move animation. You can see that the knight moves forward, while the horse runs in place, and the knight's sword is pointing downwards.

We will be extremely grateful for any help! Thank you!