I have a Whirlpool dryer LER5848EQ5 inside the house, with the vent going up the wall, into the attic, and then out of a vent on the roof. The portion of pipe in the attic has a concave bend to it at one point creating a low spot.
Recently, we started noticing that the dryer would quit before drying. I'd restart it and it would sometimes immediately shut off, or sometimes go the full cycle without stopping. Cycles were getting longer when they completed, and no more lint was on the lint screen.
I checked the screen on the roof vent and it was not clogged. So I started the dryer in fluff air mode (no heat), and went into the attic. I heard gurgguling sounds in the line where it had the low concave bend. The line there was full of water.
I removed the pipe from the roof vent and drained it. Lots of water and lint came out. I then hooked a leaf blower up at the dryer side of the vent and blew the line clean.
Now the dryer is drying clothes much faster than ever, and the lint filter always has lint in it. However, occasionally - like every 8th cycle, the dryer stops before completing the cycle. I've checked the line again, blown it out again, etc. but it shows no signs of being clogged. Possibly before, when the line was clogged, I damamged a heat sensor, but I don't know how to verify this.