Try opening the pressure release valve for an instant and close it immediately. Sometimes this will reseat the valve plunger and stop the slight leaking. Of course, be extremely careful not to get burned with the hot water spraying from the valve when it's open for an instant. Also, a few light taps with the handle of a screw driver on the flip latch of the valve will also seat it and stop the dripping. Try the tap on the flip latch before you try the instant open, be safer and less mess if it works!
PS- take the pressure off the system with either of these processes for best results!
Days camping (2015)----88 days
Days camping (2016) ---110 days
2016 Wildcat MAXX 28RKX (33' TT), 2007 13' Scamp
2015 Ram Laramie Hemi
30 years RV'ing
12 different RV's