System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: Intel(R) UHD Graphics Intel 4.5.0 - Build 26.20.100.7463

Blender Version
Broken: version: 2.92.0 Alpha, branch: master, commit date: 2020-12-24 19:11, hash: rBaf316d276144
Worked: (newest version of Blender 2.92 that worked as expected)

Short description of error
[2.92 blender, GREASE PENCIL Custom Brushes data blocks is not being saved after entering fake user]

Open Blender 2.92, on the splash screen, pick 2D animation. Next, go to brushes pick F marker Bold. Next, go to Property Editor and pick Active Tools and Work Space Settings, there you should see the Active Brush click on the down arrow under the picture of the brush now press add New. A new Brush of the same one should appear but with numbers, so you should rename the brush something like "flower. Now go to Material and add a new material rename it flower. Scroll down descriptions to be linked to flower material and pick your Stroke. In which I picked line mode type, next pick Style of the line I picked Texture. After texture, a drop-down menu popped up for me to insert a picture for my texture. Since I named the new brush flower, I picked a picture of a flower and It worked. In the picture drop-down menu, I saved a Fake User in order to save the data. Still, in Material Flower I can see my Brush, since I have tried this so many times I started saving the data by picking Fake User there also. Next, I come out of Material and go back to the Active Tools and workspace in that menu I click on Brush Settings under there I click on the Pin icon that links my brush to my material. Next, I click on the arrow and a menu pops up so there I also added a fake user to save the data. Now I go up to the Picture of my Brush and click on it and a menu pops up also with a file I clicked on it and it took me to the File section where I picked a picture for my new Brush. I then proceeded to save it as Default Start-Up. I shut down Blender and restarted it and my New Custom Brush turned white no picture texture. I have tried this many ways and the Custom Brushes is not staying put in Blender GREASE PENCIL. 😥