Why does my pump pressure not go past 3 bar

Machine owned 2 years. Same fresh roasted beans, same grinder and same technique used consistently.

Recently the machine has struggled to rise above Bar 3 on the dial when expressing a shot. It used to be around Bar 9. Grinder and tamping adjustments have had little positive effect, and now a normal tamp has the machine struggling to produce the standard shot volume. Can anyone suggest the obvious culprit/s? Is it a repair that can be done at home...? .... as we live some hours from the nearest Breville service centre.

Thankyou for reading...