After a few days of repeatedly having brushes corrupt and not be able to load them, I figured out my large textures were a little too large. Most of Krita's patterns are ~100-150KB whereas mine were up to 14MB. Compressing the hell out of them down to around 1-4MB seems to have not impacted the results any, and they no longer corrupt.
Still, saving brushes is weird, 'cause it'll temporarily save changes to the brush you used as a starting point for your new brush, and then I'm wondering why there's two of the same brush! But resetting the last brush to its last settings fixes that; it's just a bit confusing. Add on top of that that between the Linux and Windows Krita versions I have, the devs changed the format of the brushes in an update, so that compounded the confusion as to why things weren't quite as simple as copying over.
I made a "bundle" of these brushes that you can import via the Resource Manager in Krita and create to your heart's content. At least I think that's how bundles work, I'm really not sure. Anyway, thanks for hanging around and take those as a token of gratitude. I've also been taking more "seriously" how I organise my sound effects, so one day there'll be some sort of sound pack possibly.
When it comes to sound effects, and brushes to less of an extent, I feel once they become prevalent enough to become recognisably "stock" or "preset", they ultimately end up damaging the plausibility of all media created with it, even retroactively. Even the first publicised record of a perfectly good stock/preset's use will be cheapened by the thousands of occurrences that follow (like D50/M1 samples). So that's why I feel I can't share all my stock, but I don't see why I shouldn't share the methods. That way everyone will end up with a slightly different (and unique) set of their own materials. Anyway, point being, I encourage tweaking so these presets are your very own!