This might be a drag...but:
I would start with the simple things to check first.
Set aside some time to trouble shoot.
wash the mask with Dawn (original formula), rinse it till you can feel it squeek! Then dry it carefully with paper towels.
Do the same thing with your face. It should squeek when you run your wet finger tips over it.
No moisturizers or anything. We want to intentionally de-grease your skin/mask mating surface.
(yes it will dry out your skin if you do it right but first stop the leaks!)
Got all that done, put on the mask, the silocon cushion should actually stick to your face.
Now do a full pressure fit test. You should keep making small adjustments till there are zero leaks.
Take deep breaths & exhalations whil turning your head left, right, nod up & down to see if
any seals pop loose and start hissing.
Loosen and retighten straps if you still can't stop the leaks.
Sometimes a weak spot will show up when you exhale forcefully.
Find out what it takes.
I have been able to seal some pretty stubborn masks this way.
When you get a good seal you mask will only be leaking from the exhaust ports. (normal) at 12cm that might be around 35 lpm (litres per minute)
Try this with each mask till you find one that seals perfectly or leaks the least amount.
Without seeing an oximeter run for that night its hard to tell...but I would guess that you are
going into desaturation because the machine can't maintain pressure.
Which brings us to....
Next (less likely) possiblility:
The CPAP is just a machine and sometimes they break down.
A wearable logging oximeter would help right now to figure out if you are going into desaturations during the leaks.
(if they are long enough duration)
It will also show you how well the CPAP is actually doing its job.
If you are seeing reports from SleepyHead that all is well but your Oximeter readings are caving in
then you and the CPAP need to go in for a check.
The machine, to see if it is going bonkers and
You, to see if you are developing central apneas that the machine can't compensate for.
In any case keep using the CPAP, since some is still better than none at all.
Hang in there and good luck! Let us know how you're doing!