I had the same problem. It was caused by two different issues.
First, there are two small hoses going to the hydraulic pump drive. These had rubbed through and were spraying a small amount of hydraulic fluid.
I had new hoses made at NAPA to replace the originals.
This is a link to the post with a few pictures.
The second issue was the hydraulic pump is lubricated with transmission fluid and it was allowing ATF to pass into the hydraulic system. It would then overfill the hydraulic reservoir and vent out the back. Several other Monaco owners have had this issue and they recommend new seals for the hydraulic pump. I removed the hydraulic pump and installed new seals.
Installing the new seals was easy but loosening those large hydraulic hoses was a real bear. I had to purchase a large wrench set and use a big hammer on the wrench to break the B nuts loose.
Link to a thread on rebuilding the hydraulic pump.
Hope this helps.