With the newest update of Illustrator (25.3.1) all of my custom brushes are no longer working correctly. I have brush sets that consist of different colored elements and when I go to change the brushes it either does not change to the selected custom brush or changes to a brush that was not selected. Since I am now not able to complete my work, I switched to a previous version of illustrator(25.2.3) and I am no longer having this issue. Any help with this would be great!
Sorry to hear about your experience. In addition to the workflow, as asked by Monika, would you mind sharing if you saw this behavior while working with a specific file? Did you try resetting preferences of the app? This information would help us assist you accordingly.