maybe you are using fans that have a zero RPM feature, and they stop when the fan curve goes too low?
What fans are they?
Noctua A12x25
I am pretty sure it is not the fan curve problem,
It is the stupid safety measure OCTO/aquasuite use, when it detect 0 RPM for the fan but it is delivering power, it will keep turning up and down
since my splitter doesn't provide RPM info to OCTO, it always detect 0 RPM therefore the fans kept going up and down