Ahhhhhh ha from your last post I would not be surprised to find the fault being a broken off or very loose hanging anode rod or dipper tube in the cylinder itself – if these were at fault then the noise would only be evident when hot water was being run or when a hot tap was turned off.
These problems on a new cylinder would indicate to me that it had been mistreated when being transported. Both of these components can be easily changed or checked as they either screw into the cylinder or fit inside one of the water connections.
The problem you have explained is less likely to to be pressure related but more something amiss within the tank itself.
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