Hi,
If it's a Truma Avent, ours did the same thing. We found ours was not fitted square from the factory and had shifted, allowing the water to come in from the roof through the air-conditioner and onto the floor. We aligned it and never has a issue again. Also check the 2 drain holes don't have anything in them. They are located on each side at the front of the unit on the roof. Wasps, bugs and spiders will block or restrict these drains. On really humid days, you will get some condensation on the inside.
You can also remove the inside cover by removing 6 Allen key bolts to get a good look at the allignment. You will need to disconnect the connector for the base unit after removing the 6 bolts to remove the bottom cover.
Once removed you can also see if there is anything on the condenser causing water to come in.
Cheers
Nick