schmerg The safety calve is easy to fit, if you paste a photo of it with the case off, I will identify the component for you. From what you say it sounds like the safety valve…this is easily confirmed if steam doesn’t escape when the boiler is not on.
In my pre-production MK1 I have circled the safety valve in red…..it should be the same in your machine, but just in case it’s not.
It’s easy enough to remove, but if it’s got thread locker on, shock it off, don’t try and torque it off, you you may bend/snap the fitting.