Headache and slight nausea using fisher-paykel-vitera-full-face-mask

I recently received a new AS11. My Medium F20 masks type I have used since 2016 is not sealing well even using REMzzz liners (20-40% leak rate). My DME suggested I try the Fisher-Paykel-vitera-full-face-mask. However, after about 1.5 hour I woke up with a terrible headache and slight nausea. I tried it twice with similar results. I rarely have headaches. I am a mouth breather. I experienced a somewhat similar issue with the Fisher & Paykel Evora hybrid mask ... wake up 3 or 4 times per night with a headache but no nausea. I suspect that these masks do not have sufficient evacuation leak rate at my 12-18 pressure range and that CO2 buildup is the cause. Leak rate is good for both.

Have others experienced this with these masks? or any other thoughts as to the cause?

Just guessing, but wearing your mask too tight can do that.
Look at mask fitting videos on youtube.
I am sensitive to tight-fitting clothing around my head and neck,
and feel ill when a hat or headband is too tight.