Win 10, GTX 1080
Blender 2.80, 2019-01-14 19:48; 84c06e996a7a
Open attached .blend file.
Switch to Eevee and press play. You should see the problem. There are two thin meshes:
With default settings (Distance 0.2m, Factor 1) AO flickering is barely visible:
However when you increase Distance to 1m it becomes noticeable. Youtube compression is very strong, but you should see flickering:
When you additionally increase AO Factor it's even more obvious: