I have never used act on the hobbyzone planes but i have read in these forums that ACT causes more crashes than it saves. I can't tell if the 'fly away' was due to act but maybe something dislodged from the last heavy landing. That is why a range test is recommended before flying planes. Double check and make sure all linkages are still on, make sure rudder still works properly, and do a range test to make sure all the components are working properly at a distance.

The hobbyzone/parkzone planes are easy to repair, just need foam safe CA glue and tape.

Hope this helps