[rvcycleguy]

Best way would be to remove factory caulk material and replace with new. Even go so far as installing a flashing material. Water leaks, on any RV, and specifically on the TM can lead to internal damage that may not reveal itself for months, years.

Generally a surface applied product over top of the factory sealant is temporary. Especially those " as seen on TV " products. Takes time and patience to do the best job. The prep work taking it down to a clean surface is crucial to any new product adhering and sealing. Then, you may think or consider covering the TM in those critical vent areas when the camper is parked , stored in direct sun for long periods of time.