Good idea Taylorbob.
Also check to see if the carpet (in the step well) is getting wet when you drive in the rain. This might cause a musty odor. I insulated around the outside of my step well. Helps to keep the heat and sound (and water) out. You could silicone around the seams of this well (outside and under the RV).
2017 Axis / 25.4: Big Foot Levelers, Aims 1200 Watt inverter, Ceramic Window Tint, Full River AGM 6V batteries, Front Hellwig Sway bar / Rear Track Arm, Safe T Plus Steering Stabilizer, PD 4655 converter, Hard Wired Surge Guard, WEboost + WiFi Ranger, LED Headlights/Driving lights, TPMS, Surge tank, Tornado flush, Viair Compressor