Movable light flickering shadows on movable mesh

Posted this on the answerhub, but thought it was worth seeing if anyone here had experienced anything similiar :-

An issue appears to have crept into my UE4 project since updating to 4.17

It seems that movable lights are causing flickering dynamic shadows on movable meshes. This doesn’t appear to affect static or stationary meshes from what I can see, and also doesn’t occur when the lights are set to static or stationary.

Please see this video as an example in a new, barebones project -
Please see this video as an example in my main project -

Anyone got any thoughts as to what might be causing this?