We have found an issue with Copter-4.0.4’s Acro mode that causes the vehicle to be very sluggish in it’s response to Pilot input.
Please do not fly Acro with Copter-4.0.4. Other flight modes (Stabilize, AltHold, Loiter, PosHold, Auto, etc) are not affected. Earlier versions including Copter-4.0.3 are also not affected.
Copter-4.0.5-rc1 will be released early next week (Mon Oct 5th) with a fix.
Thanks for your patience and understanding.