Noticed not really been much HF action when starting up so was just having a look and there's actually something arcing out in the machine. Is this rightright?
I'm not an expert but I think you get 2 types of hf ignition inside.
1) where there is a set of points and the spark jumps the gap. In this case you would see a spark in there somewhere.
2) controlled by a hf board. In this case there shouldn't be a spark and if there is it's leaking to earth and will make striking difficult but could cause serious internal damage to other components.
I'd take off the cover and investigate where that is happening. If it is jumping where it shouldn't you can easily insulate it away. I'm no expert though I go by reading the experts posts.
I had same problem on my ac/dc 210
I played around for ages but knew there was some thing not right. Mine was better on dc than ac. I sent it back in the end and came back like a different machine. Very strong hf on her now. Give r tech a ring they will sort you out. Even send them the video.
Ref your video, You use to see much the same on old TV's from the HT area of the pcb /coil. Could be caused by breakdown of insulation or damp causing tracking as HT loves to find the easiest path to ground.