The range wouldn't be too tight if the machine didn't want or need to go higher but it does want to go higher so you need to let it.
CFlex or AFlex are just forms of exhale relief and won't increase the pressure but in fact lowers the pressure just a little bit upon exhale. You want more pressure...not less.
When we see times where it's obvious that more pressure is needed when compared to other times of the night where things are going along just fine...2 main culprits. Supine sleeping and REM stage sleep.
Normally REM isn't as prolonged as your clustering of events show the duration so my first suspect would be that you were on your back during that time frame.
REM stage sleep isn't that prolonged in normal sleep cycles.
Whatever the cause...your machine wants to go higher and how much higher we don't know.