I think that accidentally I pressed some key, and now all I can draw is straight lines in this way.
I'm using a digital tablet, the other texture in this same scene paints correctly.
I don't know what function I pressed, help.
Maybe you accidentaly changed the paint stroke method to Line. Press E in the UV Editor window and change it to Space or do it in the Paint Stroke panel.
For other useful shortcuts please see this answer: Can I paint a texture within the UV viewport?
I found that the problem was the image texture resolution that i was using. (like 4000x4000 that was the problem), I scale that image to 1024*1024 and the brush work correctly. I was aware of the "stroke method", but there was not the problem, since it was in "space".