This on going problem has been in several shops and every time the report is the same. The O ring was leaking and the pump and tank are ok. The first two times it lasted about 6 months. This last time it did not leak for a year. It just seems like a poor design. They could have mounted the tank on the tray and used a hose to move the ATF as this part is not under any pressure.
I know that Lippert dosen't make trailers but they do make the frame and I will watch for that when we buy our next trailer. I am thinking about electric slides. I know that they have problems also but electricity dosen't make a mess like an oil leak. Just a few ounces goes a long way when you have a leak. I now have over $200 in O ring repairs plus two batteries because I can't just replace the one. The trailer may also have a charging problem because when I noticed the oil on the leg I could also smell hot battery. I don't know if it was because of the short or if the charging system was over loaded beause of it but the batteries were both boiling and probably had been for several days. The trailer is always plugged in.
If we were on back roads a lot I could understand but our trailer is probably on the road a lot less than most. It goes to Az in the fall and stays parked in the same spot until spring. We take it to Idaho in the spring and park it on our river lot until fall.
I am aware that all things have problems. We have been through AC problems, a very expensive refrigerator issue, the furnace quit last winter, and the ever present oil leak. The Montana part is the only part that seems to work.