waste smell in the RV

Make sure you have water in all the p traps (sinks, showers etc), replace the check vale/air admittance valves under the sinks (inexpensive), run water down the roof black/gray vents to insure they are clear. Clean the black/gray tanks. If that doesn't fix then consider replacing the toilet sealing ring.

Sometimes the vent pipes will drop from their proper position into the tanks which means they no longer vent properly - doesn't happen often but it does happen.