@Voronwe13 is right, if you can, please check if you can import those brushes using Manage Resources → Import Resources button in Krita 5.0-beta2, if it works, then please just use a workaround before Krita 5.0 comes out officially.
To test Krita 5.0-beta2, please first backup your stuff: Help Krita improve with structured Beta Testing of the new resource system in Krita 5.0 - and after you back up your resource folder, it would be a good idea to remove the brushes you want to import from the resources folder so it’s more like a new experience for Krita. And then you can try to import them again (if the first one didn’t crash) just to see if they maybe crash on that second case when the brushes are already imported 