Condensation on cool surfaces in the heating period is no deficiency.
The ambient air enriched with increasing humidity in the interior of the caravan / motorhome, (by dispensing from the human body, also by cooking, etc.) with simultaneous expansion of this air as a result of its heating, seeks cold surfaces in order to get rid of the moisture and to settle on it in the form of water drops.
This circumstance can only be stopped by adapting behaviour, in particular by providing fresh air from the outside before and during the heating phase. Regular shock ventilation is essential, even if it is still so cold outside. This process is completely normal building physics(*) and can also be clearly observed in residential buildings, especially in kitchens and bathrooms. There, too, this situation can only be met by fresh air circulation.
(*) Condensation refers to the process when the moisture in the air becomes visible water droplets. Cold air can absorb less water vapor than warm air. Condensation occurs whenever the air cools down. In order to reduce or avoid condensation, adequate ventilation and sufficient heating must be provided.