It should NEVER smell inside the RV when dumping period.
Do you have water in the bowl of the toilet?
Has the water in your p-traps in sinks and the shower evaporated?
These are the 'only' access points inside the RV that can allow tank smell to enter your RV.
If you don't use the sinks and/or shower often and it's hot outside the water in the p-traps (which is there to prevent smells from coming into RV from tanks) can evaporate and allow the smell up into the RV. Run water into all your sinks and showers to make sure p-trap is filled.
The toilet bowl should 'always' have water in it.