Hmm tried downloading from github but get an error when enabling the addon. Guess I will wait for next release. Thanks for responding, glad to know it's getting fixed.

Ah so it is a problem of vertices being essentially on top of each other that belong to different bones. Is there any fix for this or do I manually need to fix the weights? As I said above this is certainly not the first time I've encountered this and was hoping there might be some easy way to fix without painstakingly fixing it manually, it can be a big task with denser meshes.

Most models I import into blender work just fine, however I have noticed a few have issues where it looks like nearby bones get their weights blended together or something like that. I am not sure if I am doing something wrong, but this is not the first time I have seen this. Recently updated to the most up-to-date source tools addon and blender 2.82a. Problem still persists.

https://gyazo.com/b4c346dca6bf4198d74469b93e201c29
As you can see, the engineer toolbox weights are imported wrongly and it becomes a stretched mess when opened. I decompiled the model/animations with the most recent version of Crowbar.

If it makes any difference, I have noticed the same thing happen on the portal 2 test chamber door model. When opening the two halves of the door parts of one side stretches to the other because of incorrect bone weights.

Thanks.