This is probably an artefact of the way the animate command displays a series of PPM images. What happens is that OutputPPM generates PPM images which are just big enough to contain all the data in your simulation e.g. if you use 7 levels of refinement and one box, OutputPPM will generate images with 128x128 pixels. If you use an adaptive resolution with a maximum level of 6, the size of the resulting image generated by OutputPPM can be anything in 1x1, 2x2, 4x4, 8x8, 16x16, 32x32, 64x64 depending on the maximum number of levels necessary to verify your adaptation criterion. As a result, animate can see a series of PPM images with a variable size, if you look carefully you will see that the weird patterns you see are smaller-size images of your simulation, displayed in the top-left corner of the initial image. What animate should really do is blank out the previous larger image before displaying the smaller image, to make the difference in size clear.