MuddyOne - I can see the shot starts well, and go wild/deteriorates halfway through. questions:
- how old are your beans?
- how old have they been inside that air escape?
- where are they kept? (Same room?)
- what basket are you using? (Assuming VST 18g?)
All I can think of is that your coffee is well past their best. This could be where they are kept if the environment is too hot, or temperature fluctuates. I see for example your machine and grinder are right in front of a radiator. This is not the best idea.