Warframe Shader Caching

This is a Proton-version-agnostic issue, more (assumedly) on the Steam-side of things.
Shader Pre-Caching is a great feature, but for Warframe specifically (a couple others come to mind, but none as egregious as Warframe) it is utterly broken, downloading and compiling new shader caches daily unless the Shader Pre-Caching option is completely disabled.
This used to be a couple hundred MB, but has ballooned to 14GB of daily downloads, that don't seem connected to any updates of the game itself. At that size Vulkan shader processing also takes massive amounts of time, each time.
The issue has been raised in various places, Steam Community, Warframe Forums, Reddit, some of these going back two years.
Whether there are video files erroneously being re-downloaded, or some other major bug, this is a wholly unnecessary stress for the Valve servers and client PC's.

The report names no Fossilize file, test, or entry point and attributes the behavior mainly to Steam-side shader pre-caching. Start by reproducing the daily Warframe cache downloads and tracing which Fossilize serialization or Vulkan-cache path is involved; done would require identifying a Fossilize-related cause and a focused way to verify that repeated downloads stop.