What version of Blender are you using? I have no problems here with 2.79 or 2.80. Uploading your blend file would help.

These could be delta animations which are designed to be played on top of other animations.

This is unlikely to be an issue with the importer.

Thanks!

That's the sort of thing which may well be happening. I'll take a look when I'm next able.

Flex animations are only a thing in SFM, unless something has changed since I last looked.

Even if you are using SFM, you can still export files which will be compiled by studiomdl. That's the issue here.

The 2.80 API is supposed stable now, so I would start there. The addon won't change much as the upgrade work has already been done.

But do consider the fact that I'm reluctant to put anything specific to Source Filmmaker into the tools because it's confusing for everyone who is targeting a normal Source engine game. I would strongly suggest creating an addon of your own which depends on the Blender Source Tools, instead of editing the tools themselves.

You can now find a beta release for Blender 2.80 on GitHub.[github.com]

I'm working on it. There are some bugs that need to be fixed in Blender first.

I didn't know that was a problem. Might explain how I've struggled to repro the issue. I'll take a look after I finish the upgrade to 2.80.

It will be. I'm part-way through the upgrade.