Disassemble everything.  There is a pressure seal which includes a TOP cap 0-ring that if it gets dislodged or missing, bad things will happen.  It's not easily noticed, honestly, I only noticed mine when the husband accidentally dislodged his.  It's not always very well seated and easy to lose. That's about all I can think of, given what you are describing.  Make sure your orings on the drip tip are there too.  Good luck.
Anna
	
		
			
		
		
	
			
			Anna