Back on topic (let’s face it, coffee machines and coffee forums in general are a first world problem), I just checked my Elizabeth and I can now say 100% my machine suffers from the same issue. Mine dates 30th June 2020, one of the first V3 machines and from the very first V3 shipment from BB.
The first shot is always around 10 bar. All subsequent shots are 9 bar. Today I backflushed the machine first and then the subsequent shot was at 9 bar. Contrary to some advice given, flushing water through the group does not contribute to anything but to water wastage.
I never really noticed because I always pull one espresso in the morning and one after lunch, so, to me, the machine was always consistent, as I seldom pull 2 shots in a row.
Oh well. Looks like this issue was there from day one.