Help with a wavy surface wile sculpting

Friends, I’m still not very used to Blender’s sculpting mode, I was doing this kind of stylized cliff, for a scene I’m creating. But I don’t know how to explain why this happens, you can see this surface that becomes wavy, especially when I use the scrape or flatten brush. Would that be too much resolution on the mesh? less resolution? Is this the brush behavior? If you can help me it would be a big help.
Thanks in advance