Black Tank Overflow

[lifeontheroad]

So I've been having issues with my black tank since I brought it in for service a couple months ago. First, it was smelly. I used the holding tank treatments and kept an eye on the gauges to ensure it was dumped appropriately, but it would still smell. I started dumping it more frequently - maybe at about 2/3 full - and that seemed to help. This week however, things have taken a turn for the worse. My black tank is now leaking into the toilet.

1. Usually living by myself, I empty out the black tank once every 5 days or so. I am a bit cautious about overfilling it, so I try to find a good balance between letting it get too full, and not having enough water in the tank to dissolve the solids.

2. I emptied the blank tank out on 9/10/19 before my fiancee moved down. I flushed the black tank and kept the valve open for a bit to let it fully drain. I then shut the black tank valve and drained the grey tanks.

3. During the day on 9/11/19, my fiancee opened the toilet to go to the bathroom and there were solids in it. He went to flush the solids down and rather than going down to the black tank like he thought they would the toilet overflowed. He realized the reason they were in the toilet to being with was because the tank overflowed in the toilet. When he added water, the toilet overflowed.

4. I ran outside and pulled the black tank valve. It was FULL. He stayed inside and cleaned up the mess.

5. After that occurrence, we have been watching the black tank quite meticulously.

6. Yesterday (9/13) while I was at work, my fiancee emptied the black tank again. He did flushed the black tank with the valve open the whole time.

7. This morning (9/14), we woke up to find the black tank had overflowed AGAIN. There was water around the toilet, and down the wall in the back. It leaked into our basement.

We are quite puzzled why this keeps happening. Neither of us are using the bathroom enough to justify this situation. This morning, we opened the valve, flushed the tank, and then disconnected EVERYTHING from the city water. We are now using our water pump and fresh water tank for everything.

History:
1. Purchased NEW 2018 Keystone Montana 3721RL from Camper Clinic II in Buda, TX in July 2018.

2. Lived in mostly full time in Zapata, TX from July 2018 to May 2019.

3. Lived in mostly full time in San Antonio, TX from May 2019 to June 2019.

4. Took into Camper Clinic II for yearly maintenance in June 2019. Returned to same campground in San Antonio, TX after two weeks and stayed until August 2019.

5. Moved to Mathis, TX August 26, 2019 and have lived in full time since then. Only started having these issues this past week (9/10)

Anybody have any idea what could be causing this and what we can do to troubleshoot it? I don't have a truck to pull the camper, so taking it in somewhere becomes quite costly! Would prefer to try and identify on my own and then have a mobile tech come out to visit.

I also have the RV Forever Warranty. Does anybody know if they would cover this?