Code used library reloading which would reload all data-blocks from a
data-block library. Since the essentials brushes are stored in a single
.blend file (one per mode), they would all be reset. In general this
violates the design where multiple brushes in a single .blend file
should be usable just fine. (A single file per brush is only necessary
to allow saving edits to that file without opening it.)
Instead of library reloading, delete the brush from the current file and
re-link it.
The link/append API should probably get support for reloading a single
data-block (and optionally its dependencies) but for now this is not
supported yet.
Pull Request: https://projects.blender.org/blender/blender/pulls/129866
fd2d2f225f