The answer to 'sod erosion' is that it is a common problem that occurs when the soil under your lawn becomes washed away, causing the grass to become loose and unstable. This can happen due to heavy rain, irrigation issues, or poor soil drainage.
Some common symptoms of sod erosion include visible gullies or divots in the lawn, grass that is pulling away from the soil, and muddy or wet areas that don't dry out properly. To address sod erosion, you may need to re-grade the soil, improve drainage, or replace the affected sod. In some cases, you may be able to DIY these fixes, but for more extensive damage, it's best to call in a professional landscaper.