Hi, and Welcome!!
Likely loose connections - tighten and problem will likely go away.
Be careful on the nut closest to the gauge; I think spinning the threaded stud may cause internal damage - hold it while tightening the nut.
See this for diagram on how stiffen things up:
(Courtesy of SOBill (Bill Taylor) at: http://www.poca.com/index.php/gallery/?g2_itemId=6585
Larry
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