There is the possibility that towels and sheets are made of different materials. Towels are usually made of cotton or other absorbent materials, while sheets are typically made of synthetic fibers. This material difference can cause the towels to absorb more water than the sheets, resulting in an unbalanced load. Towels are generally much larger than sheets. So their size could also be one of the reasons for the unbalanced load. If your washing machine is vibrating excessively, you will need to redistribute the load to be evenly balanced.