This is an issue is been covered but I thought I add my 5 cents worth of experience.
I start to work only with rotary a bit over 9 years ago and with only the dragonfly over a year ago.
I noticed like everybody else that own one that after few months of use keep getting louder.no matter of which needle get used .
So I try to find a solution .
This is what I ve done :
- take the cap off and unscrew the give adjustment until u can take the spring off
- take off the piston as well ( after unscrewing the grub inside it )
- take off the little rubber dampening noise thingy ( all mine were broken )
- clean everything with alcohol
- I replace my rubber with a new one ( but a black one from a hardware store ) .
Is slightly stiffer but dampen the noyse much better
- replace the rubber inside the piston housing
- I used silicone grease lube inside a syringe and fill the hole inside the rubber and a bit around it with it
- use a bit of the same grease around the piston and put the machine back as It was previously
- use a bit of grease inside the oval window where u can see the outer case of the piston
- normal service ( a bit of oil on the 4 corner when the piston is pushed down close to the dampening adjustment as explained in the manual ) .
- run it for 3 min at 12 volts
- clean .

Now is better than new . Work perfectly and is nearly noiseless .

Hope this help somebody .

Keep up the good job