If the model in the broken smd file was was constructed properly, the the idle animation smd would look like this when it was applied. (speculating this is what you're looking for)

https://i.imgur.com/PUhSvps.gif

The animation isn't broken, the model is.

You posted 2 SMD files, one broken and one idle.

The broken one is rigged with bones but doesn't have any animation data in it so it just sits idle.

However, the idle smd only has bones and the animation in it (which I believe to be your animation model.)

So when imported the idle animation onto the mesh in the broken SMD, flips around like your image did.

So, the problem isn't apparent to me because I don't have the .blend file or a sample gif with the correct animation in it and don't know what these things (the panels) are actually supposed to be doing or why you think it's broken.

However, digging a little deeper into what I do have, I did find this...

https://i.imgur.com/Abe1WWK.png

https://i.imgur.com/Ushhjrp.png

I don't think it was BleST that broke your SMD, I think it's a modelling process problem.

https://i.imgur.com/bNjSWaQ.png

Yeah I know Zappy but I went to download the model to see if it really was a problem but the link is just a picture not a model.

SMD and DMX are both Source Model data and need to be compiled with a QC to work in the source engine. They are the same thing really, SMD is the old clunky format and the DMX is the newer more advanced format. So again, why does it have to be SMD? Also, you said you linked a model, it's nothing more than a picture.

Why does it have to be SMD?

Rename the 2.83 folder in the Appdata folder to something else (don't delete it), Roll ahead to Blender 2.83.5, Launch it. This will give you a vanilla version of 2.83. DON'T import settings from previous versions just set up your left/right select and the spacebar activities then save user settings.

Now that you have a vanilla version running , download and reinstall BleST 3.1.0 from the Steam Review page ( https://steamreview.org/BlenderSourceTools/ ) and try your Export. It may be an old add-on causing the problem from your previous settings.

Did you upgrade to 2.80 from and do you still have the Blender 2.79 folder in your Appsdata - Roaming - Blender Foundation - Blender folder?

If yes and you had BleST 2.10.2 installed for 2.79, use the Steam Client- Software Library - Right click Blender - Properties -Betas and roll back to 2.79. Does BleST error out when trying to use 2.79 to export an object?

If you're getting the same error from that or the blender object doesn't export, then it's something other than Blender and BleST that is causing the problem.

If you get a good export, Roll ahead again to the Current version by opting out of the beta and allow Blender 2.83.5 to reinstall then try again. (we can see that BleST is installed correctly for that version, of it would not appear in the Scenes Tab of the property panel)

Nope, not the problem, mine is exporting perfectly, both collections and suppressed.

Does folder N:\test actually exist and is it a valid mapped drive?

Another thing,

Operator bpy.ops.ed.undo.poll() failed, context is incorrect

This is a blender function, have you remapped the UnDo function somehow?

Oh no... Blender 2.83.5
Blender has updated again... and I'm not sure when that happened.
Hang on, let me see if I have the same problem now. (shouldn't affect anything from 2.83.4, but you never know.)

That looks like it is set up properly for SFM. Would have liked to see the actual model you were trying to export though. When exporting how many vertices and do you suppress the collections before exporting the model files?