The bane of my existence are the tip curl/fray/fishhook
https://www.dakkadakka.com/dakkaforum/posts/list/789939.page
There are 2 reasons:
1-For a good detail brush to hold the point it needs to have all bristles come to a single point, and not be "trimmed" into a sharp shape.
2-Natural bristles are superior in performance to the synthetic.
I would take a guess and assume you are using synthetic brushes.
The tip problems do not happen with natural bristle brushes, and if it does, they are repairable with hot water and hair conditioner.
Kolinsky / Sable might cost you 20 - 30 monies per brush but are worth it.
I like to use cheap tools, but a good brush, I need to have at least one.
I find my self grabbing my remaining 2 sable and 1 kolinsky brush whenever I paint. All of my detail and highlighting for past 2 years has been done mostly with these 3. They look janky now, but when load em up with paint or thin wash, the few hairs that remain do come to a point. Hope this helps.
Also, the guys from YouTube videos, ether new synthetic brush, or most likely a very nice Sable or Kolinsky brush.