Black tank

[skyviewman]

We have a 2008 3400RL and we are having problems with the black tank. I have done a search but cannot find an anwser to our problem It seemed to start as though the pipe going into the tank was blocked. When we pushed the lever to flush there it seemed as though the toilet would burp and the water would go down. I couldn't see the water in the pipe but if I filled the bowl with water and pushed the lever and listened in the basement I could hear the water slowly going into the tank. I used a snake to see if there were any blockages but came up empty. I then emptied the tank and filled the the pipe and the toilet with water and used a plunger and all of a sudden the water went down in a rush as it should. I then put a couple of pails of water into the tank and some digester and only used the tank to p without putting any paper down the toilet and left it for 6 days. When the toilet was full of liquid and started to burp I draned the tank and flushe it real good. The gauge read 1/3 full and we started to use the toilet normally and after the second day it started to burp and was as it was before. Used the snake but only got out some toilet paper, checked the roof vent to make sure it wasn't blocked, drained the tank and filled the pipe and toilet with water and used the plunger. With the sewer drain open and using the plunger the water went down and right now it seems to be working although we are only using it to P without putting the paper in the tank. Any suggestions on what the problem might be or what I could do next would be appreciated as I have a feeling that the problem is still there.