An F10 should not leak so much at 9cm fixed. I am assuming that it was working fine for 5+ months.
Things to evaluate/try:
1) How old is the mask cushion? The silicone may start breaking down.
2) have you Adjusted your straps' tension lately. They may stretch over time and your goldilocks setting may have moved due to this.
3) when the machine starts, do you lift off the mask a little bit from the face to let the silicone seal to inflate?
4) are you tightening it too much? In my experience with F10, I would tighten the top 2 straps snug and the bottom 2 were left much loose.
5) Have you tried mask liners? In my experience, they made the whole Process much manageable. They eliminated the need to shave before masking up too.
Started APAP 4-20, Closed range to 7.5-14, then straight 8.0 w/ Aflex 3
RDI always below 1. But sleep much much better at straight pressure.
Started on F10, Tried Quattro Air successfully. Finally settled on P10.