Jabsco HD Water pump (inbuilt) pressure switch issues?

[Blue Seas]

Anybody experienced an issue with the inbuilt pressure switch on the Par-Max water pumps? I have recently fitted a new HD version which seems to have an intermittent problem - sometimes it will work fine, charge up the accumulator and then cut-out as normal - other times it will experience rapid on-off cycling (da-da-da-da etc) before eventually cutting out (new accumulator did not change anything).
Suspect a duff inbuilt pressure with but before I return it I thought I'd ask if others had had the same experience?

 

[srm]

Have had similar cycling, but not so fast, without an accumulator in the circuit. Caused by a either a slow leak in the circuit or by the back up foot pumps not being isolated.