Like many things *being on site is worth a thousand words and a hundred phone calls..
Thus I am tossing up some points... *
1: Where are you.. *
2: Sounds like a group seal has split
3: Over dosing and locking to hard to the right can contribute 2 collar issues and crushed seals
4: If you have to choke it to deliver the right flow, then I would suspect that there is something not quite right in your machine or / and your method..
5: Why would you use teh rubber disk B4 and after every shot... *Not required..
6: What PF ?
7: What grinder
8: What beans ?
Baz... I had a look back and your sweet spot was around 1:00 if so and your going to RED then it could be the BEANS / Grind / Tamp.... This could also cause a problem with the seal..
I know roads are down every where... But I have Thursday and Friday up my sleeve and heading over to W/Manly at some stage.. Only too happy to drop in, or if your over Wooloowin way.. Happy to demo mine and or play with yours..