First is there seems to be two types of mask connector, one I believe is correct and works great the other causes massive air flow leaks. The good one has a cover over the ring vents around the main connector the leaky one does not.
EVEN MORE IMPORTIANT ResMed sells theses as a two part system. The frame with the connector (and its small vents) and then the replacement UltraSoft™ memory foam cushion.
This seems like great idea: BUT I discovered that these tiny vents can become plugged by our using them for a long time. See the picture with two of these connectors, the plugged one is on the left the good new one on the right.
I have been using the same frame and connector all year long, not knowing this could happen, just replacing the memory foam cushion every other month.
And lastly some of the foam can GO BAD, I am not sure why BUT I tried a new complete mask Batch 1453388and it was crap, mask leaked all over the place and bruised my nose and no matter how tight I made the straps it leaked and farted on my face.
I dug out my old mask and it works correctly.
For some reason even in its box and bag it had gone bad.
AND I found a test for the good foam and the bad, pinch it tightly and count seconds, the good foam will return to normal shape by 3 seconds, the bad ones take longer.
So to sum up: Check your connectors for the cover on the vents, check you connector for blockage, or replace it every two to three months, and lastly check the foam if it is leaking.
Rich