my worcester 28 increases from 1.5 bar to 4.0 bar in 30 minutes?

my worcester 28 increases from 1 bar to 4 bar in 30 mins the prv doesn't release so i released pressure at the prv and the pressure gauge stayed at 3 bar so i changed the gauge but the same problem occurs now and now when you set the pressure to 1.5 when cold and leave it it has rropped to.5 bar any ideas cheers
soaveboy