With the model editor, there is an undocumented way to import models from Source 1. Within that, if you attempt to import a model from Source 1, it fails to compile correctly, stating that it didn't understand the flex rules. This causes the flexes to import, but look corrupted. This is because all of the flex rules are defaulting to values like "2" which causes correctives to be way more powerful and to be enabled at all times.

This seems to only be applicable to models that have custom flex rules for certain morphs, i.e. 'HWM' models from TF2 or 'FACS' models from HL2.

Attached is an image of the flex rules being viewed in the model editor, showing the incorrect values, and a *very large* txt output from the console importing the HWM Engineer from TF2 with maximum verbosity on the model compiler.

https://i.imgur.com/tD6eZZw.png

https://www.dropbox.com/s/v98apzhtcmbz5tb/engi_console_output.txt?dl=0

EDIT: FACS models seem to have different errors, relating to stereo flexes (possibly due to flexes internally having L/R labels that don't exist in the final model compiled by studiomdl?) Attached is a build log for male_07 from Half-Life 2:

https://www.dropbox.com/s/ixqnxq3wigdlz8p/male_07_compile.txt?dl=0