Chattering is caused by excessive (greater than 3% of set pressure and no adjustment in blowdown) inlet pressure drop. It is a relatively high frequency dynamic process.
Cycling is caused by too large an orifice a nozzle size PSV. It is a relatively low frequency dynamic process.
At the top of the post in the Google search block, put "inlet pressure drop" (include the quotation marks). The radio button for Eng-Tips Forums should be selected. Left click Search. Then read the pertinent posts.