See if you can make a copy/branch of your current version and force delete the grass. It may cause a metric ton of errors and possibly a crash, but if it clears the references it might just save the level at least. Repainting a different grass will surely be less painful than the alternatives.
It might even be as simple as clearing the shader cache and letting it fully rebuild. Though I’m not sure where the cache is stored. It’s not common to see an error like that, that isn’t caused by the hardware, the drivers, or randomly failing cache of sorts.
I don’t think it will work since it seems the compression itself is failing and not the decompression.