New STI with issues

Took my new STI Spartan to the range yesterday and had it fail miserably. About 75 rounds in the hammer started following the slide forward. I've been in touch with STI and really haven't been impressed with the level of service I've received. Answers to my questions have been very vague. So, I'm going to take the time to learn how to detail strip.

My question to the forum is what should I be looking for? I'm assuming a spring broke or detached itself. But with the level of knowledge here I'd thought I would ask you guys before starting. My only apprehension here is finding the defective part and mis- naming it, costing me money on parts I don't need.
Any ideas?

There is something wrong between the sear,hammer,or the diconnector. It's not a job for a kitchen table gunsmith to fool with. Either send it back to the company or get a good gunsmith to fix it. The pistol is very dangerous in this condition. It could go full auto at any time. :smt033

Yes - they need to fix it.

Taking advice is one of my strong points and detail stripping is getting easier. I decided that if the pistol is broken and going back I could take it apart without worry. STI doesn't offer a warranty so there was nothing to void. I did get the hammer cocked once but only long enough to get the safety back in. I was kinda surprised at the simplicity. I've heard people hear say too familiarize yourself with your weapon, and we are on much better terms now. Now to figure out if shipping or a gunsmith will be cheaper.

I would try to find the best gunsmith I could that's local. Shipping would be around $50 bucks each way. If I had to ship it I would send it to STI as they may repair it and ship it back free of a charge. Good luck. :smt1099

Well, it's on the way to STI. Gunsmiths around here were looking for almost the same as shipping. STI messed up, they can fix it. They're turnaround is about 2 weeks, but I won't be able to get out till then anyways. I've got my fingers crossed.

Well I hope they due you right and they should. Keep us in the loop on what happens. :smt033

I got the info notice from UPS that I missed a delivery yesterday. It's good news it's back already, but now I have to wait till Tuesday to get it.

Picked it up from UPS this morning so I wouldn't miss another delivery. According to the paperwork they provided, the sear spring was slipping off the sear so they replaced the spring. I'm glad it's back. I'm glad it's fixed. I'm not glad I did a price check on a sear spring at Brownells. Oh well, live and learn. On the bright side I get to practice stripping it to see what a good sear spring looks like.