I dunno if this is the right place to report this, but I couldn't find a bug tracker anywhere, so here goes.
When using the brush tool in the watercolor city style, using ctrl+z to undo brush strokes reduces the quality of the texture significantly. I thought at first that the issue was my browser (firefox), but after opening brave to test it out, the exact same issue occured.
Steps to reproduce:
  1. Open a watercolor city style map
  2. Make multiple edits with a high-detail texture, such as the farm textures
  3. Hit ctrl+z to undo at least one edit, and watch as everything else turns blurry