Yeah they did that for me and it still didn't function properly.

Mine has been running great with most rounds. Only a few FTFIRE  and I am sure it was the ammo. I would get another mosquito any day.

 Just another new old guy, with an opinion. I purchased my Sig Mosquito in March of 2013 and it's a "F" series S/N, so I assume it has all of the latest updates
as of 3/13. At he present time I've fired about 2000 rounds with it, mostly CCI mini mags or velociters  . I've also run other brands of good H/V rounds with out
problems , the only ammo that didn't work well were standard velocity and naked lead bullets. Every thing else has provided satisfactory results.
The Mosquito is one of my favorite .22 hand guns, even after reading 100's of negative comments about them and I have no regrets about owning one.

           .......................................  Jack

I have an older one and once I found the right ammo, it has been great.

I bought my GF a Pink one she just couldn't live without, happy to say it runs any High Velocity crap you feed it. 1000's of assorted dubious quality rounds, just a few malfunctions mostly caused by carbon and dry gun syndrome. Don't know that I would ever trade my Trailside for 10 of them, but not a total turd as some would have you believe................

I purchased a Sig Mosquito as part of a suppressor package in 2011 iirc. It was a jam-O-matic out of the box. I contacted Sig in Exeter, NH and got a return authorization and pre-paid UPS label. They returned it in about two weeks and it has run fine both suppressed and us suppressed ever since, WITH THE RIGHT AMMUNITION. Suppressed, it runs fine with just about anything but I run CCI-SV almost exclusively. Unsuppressed, it runs flawlessly with CCI Mini-Mag 36 or 40 grain but will occasionally hang-up with any of the bulk-packs.

Would I recommend buying one? No. It was some grief to get it working right and it is still finicky.

However, it works for the intended purpose; suppressed plinking.