Bug: Flexes in L4D1(/2)/Alien Swarm/Source Filmmaker models cause near-immediate engine crash

[pivotman319-owo]

Describe the bug

Models built with ASW/SFM engine studiomdl cause the game to almost instantaneously crash (or crash upon a redraw, e.g.: looking away from it, then looking back at it) due to how Strata handles dmx flexes ingame.

To Reproduce

1. mount SFM's game\tf_movies folder or use this
2. start engine, run any map
3. invoke prop_dynamic_create player\hwm\heavy
4. Expect a crash

this additionally affects the inbox SFM model counterparts for the left4dead2 and tf hwm models; video attached below

https://github.com/StrataSource/Engine/assets/15126754/db9ce6a7-b78a-4be6-a093-5c52605adbeb

Issue Map

n/a; happens universally

Expected Behavior

The model should be displayed correctly.

Operating System

win11 v23h2 beta channel - 10.0.22621.2915.amd64fre.ni_release_svc_betaflt_prod1.231204-1534

[Gocnak]

Should be in next release.

[pivotman319-owo]

still recurring in latest QA staging branch build (13105764) with sfm tf2 merc models and a personal fursona model. reopening; refer to crash reports sent just now.

l4d1 character models confirmed working as of last week (per build 13074641).

[SCell555]

Hwm stuff should be fixed now.

[pivotman319-owo]

remanifested in staging build id 15936744, see crash report

final frame before crash: