Seen it but haven't corked it up yet. My 23B lives indoors except when camping so the likelyhood of critter entry is very low.
Stuff some caulk backer in there and top off with your favorite flavor of caulk.
2006 23B Hybrid with 10k round bar WDH
2011 F150 4x4 SCREW Ecoboost, Max Tow, Integrated TBC, 3.73 LS axle, Firestone Ride Rite airbags.