What could be eating through my drywall
Since the Pest Controller didn't find any pest cause or problem, very good news. Go ahead &amp; patch, tape &amp; mud it. Make sure the patch doesn't touch the masonry. The moisture down there may get it again or any paper break. If it starts happening all over, eventually, then painted fiberglass faced drywall would last or you might opt for cement board at that time. But, just patch what you've got to gauge what works &amp; what doesn't &amp; for how long.