Stripe pattern when using brush or eraser

Hello everyone!

It's my first time using Animate and i have this issue when i'm using the classic brush or the eraser. There is a stripe pattern when i'm drawing and the color is transparent, and it disappears when i lift my pen, same when i erase. Like it's not drawing/erasing in real time.

And on tutorials i watched, it is normal, so there may be an option but i dont know where.

Thanks