"No transducer response "alarm I cleaned Mt 50 transducer, but still alarm comes, purifier don't stop when alarm comes

In main engine Lube oil purifier 821 bowl opened for bowl cleaning after that "no pt4 feedback pressure during ti59" Alarm coming. After that i started purifier without caliberation it is running ok parameters are (pt1- 0.33,pt4- 1.3,pt5- 1.2). After every 3rd day "no pt4 discharge fe...