Either the motors faulty or Water has got into the pressure switch and causing the machine to operate late and needs replacing or shaking out.The Overide button is just that and was originally fitted to the machine they copied the VORTOPLAST when they changed over from the type 1 pressurestat to the Elbi MK11 the pickup tube was to long and didn't allow the machine to reset way back in 1986.
if you are pumping in 22mm pipe then that's the reason as they can only work in 32-40mm.
Muncher
November 2014