Just picked up a Ruger p90 in "excellent shape" for a good price. The problem is when I checked it, the pistol will only work single action. I have three other p series pistols and have never seen this before. I also cannot break the pistol down to see what the problem is. I know to push the extractor down before trying, in single action everything seems to work. I dont know whether to send it back or have a gunsmith take a look in case its an easy fix. Any suggestions would be helpful. Thank you