[MP4][AllEnv]Animated signs breaking when used on multiple block types

[dreadofmondays]

Observed this in Lagoon, but I imagine it applies to all environments. Under certain conditions, animated billboards / signs in a map will break. they will stop animating in the editor and turn black once the map is played.

It tends to occur when many different animated billboards are being used. At first I thought that it was related to too many different animation files; but on further investigation, animations seem to break when they are used on multiple different block types at the same time. If the same animation file is applied to three different skinnable blocks, only one will work and the rest will break.
Update: Further testing indicates it may be closer to a simple "too many animations" problem, or a combination of both 'restrictions'. It is very unclear.

I can't be sure this is really the reason or the best way to reproduce it, but doing that seems encounter the bug consistently for me.
You can try to reproduce it simply by placing many skinnable blocks and skinning them with many different animation files.

Anyway, please fix! I'd like to use many animations