Mine was flaky as well on a pi2 with 8.0.1. I did put the following in a modprobe config file and rebooted:
rpi3:~ # cat /etc/modprobe.d/8812au.conf
options 8812au rtw_power_mgnt=0 rtw_enusbss=0 rtw_ips_mode=1 rtw_vht_enable=0 rtw_ht_enable=1This limits the wifi to n instead of ac, so max 150mb/s, but it is stable. Perhaps it will work for you and provide enough bandwidth in the less crowded 5ghz range?
Thank you very much zaphod24, with this configuration it seems to work perfectly