Bobcat .30 advice

Hello all.I have a Bobcat MkII .30 that I bought new in Dec.2016.I am very pleased with the gun ,but last week it did something that has me puzzled. I had only shot one tin of pellets(150)through the gun (total)when I noticed that the regulated pressure gauge,which was always just a hair over the 160 bar. was now at about 156 bar.I really did not think to much about this as the gun was still grouping nicely.so I shot a couple groups and put the gun back on the shelf in my shop where it stays.Two days later when I picked it up to do some shooting I looked and both gauges were on 0 all air had leaked out.I cant remember exactly but when I set it down two days earlier,it was at about 170 bar.I charged the cylinder expecting to here a leak ,but i did not and the regulator gauge was back up to its usual hair above 160 bar. I have shot the gun twice this week (a couple of five shot groups)and the regulator gauge has fallen to the 156 reading again,but no total air loss.So I am asking if any other Bobcat owners have experienced anything similar and should I be concerned with the lower regulator pressure reading.Any thoughts would be appreciated.
Thanks Tony
 
The fact that it dropped pressure down to zero is a bit disconcerting and I would be trying to replicate EXACTLY how it happened to understand what caused it. When you "put it back on your shelf" did you lie it flat or lean it against a wall on its tank? you may need to do this lots of times. If it happens again, look for a pattern. If it doesn't then great, but you got to keep trying. Let us know how it goes