Hi Mengzhe,
Close.
We have AE0 and AE0.1 AE0.2 AE0.3 ETC ETC,
Every time we add a new AE0.X it drops the bundle for a few seconds before coming back on and staying stable.
This AE Bundle goes into the fusion switch and both ports run at 1G,
So I don't think it's a Loop,
Also we are purely migrating the configuration from our MX5 which goes into the same EX4200 Switch with a LAG and that doesnt exhibit the same behaviour.
Thanks