Had the same issue 5 years ago and got it answered 1st time in this very Forum.
yes it probably one of the diaphrams. Usually the main offender is the drivers door controller, so start with this one.
Once they start to perish you find all the diaphrams tend to give up at close intervals.
Also check the Y connectors under the bonnet where the lines go into the firewall. Common for one of these to perish also.