Only if not already created: a new tyCache object

[im.thatoneguy]

This doesn't appear to be respected. It will keep generating more and more tyCaches. 

Export Particles:

Only if not already created: a new tyCache object will only be created, if an existing one using the exporter’s output sequence as its input does not already exist. If one already exists, it will simply be updated.

[tyFlow]

Is there something idiosyncratic about your output path? Non-english characters, UNC path, relative path, etc, or something? Because in normal circumstances this feature is definitely working...

[im.thatoneguy]

Is there something idiosyncratic about your output path? Non-english characters, UNC path, relative path, etc, or something? Because in normal circumstances this feature is definitely working...

Not UNC, but is network drive. 

W:\25002 Seattle Mother Earth\Assets\MotherNature\DataIO\VegetationCaches\tyCache_tyFlow_Lashes.tyc

Is there a maxscript I can step through and debug?

[tyFlow]

The check function takes the fully-resolved input path of all tyCache objects in the scene and does a lower-case comparison to the fully-resolved output path - if a match is found, a new tyCache object is not created. If repeated exports are continually re-creating new tyCache objects with that option enabled, then some part of your output path is changing when it's being resolved...hard to guess what, though. You can test with a more benign output path (ex: "C:\temp\output.tyc") to compare whether the function is working in principle.