So...still there!
I have noticed that it is the shape of something and I can see a screw or a hole in something so it must be the edge of something reflecting back.
Also, as it seems to look slightly different in each filter, would that mean that it is before the filters, like in the flattener perhaps. I am using a WO Adjustable PFlat IV.
Ive tried looking down the tube and with the torch and the tube is very well baffled including the F/Touch focuser therefore I think I'm going to concentrate on the camera and filter wheel etc.
Any other feedback before I head up with a heap of adapters to get the right focus distance and tear it apart?
First image is green, second one is lum.