Most of the time, paint splotches are caused by a paint roller that is not in good condition. The paint roller may have been used too many times or it might be too old. There are other causes of paint splotches on walls as well. One such cause is that the painter might have moved their arm while painting and created a paint splotch on the wall. Another possible cause is that there was an object in the way of the painting process and this led to a paint splotch on the wall.