One common cause of this issue is the striker channel being full of grease and gunk. It is well documented over at XDtalk. Remove the striker, clean the channel and striker very well, and reassemble WITHOUT LUBE. It states in the manual that the striker and channel should be dry.
Cleaning the striker and striker channel is extremely easy to do, and takes all of 10 minutes. Since the XDs has no loaded chamber indicator, having oil/grease in the striker channel can cause hydraulic lock. There is no outlet for pressure. When the striker goes forward, and grease/oil is present, it can cause a light strike. Also, when you fire the gun, and the slide is returning to battery, the striker catches the sear causing the sear to be pulled to the rear of the slide, if grease/oil is present in the channel, between the striker and striker retaining plate, it can hydraulic and stop the slide short of battery. This is because you can't compress a liquid.
I had an XDs .45 with this issue. I cleaned the striker channel and it was packed with grease from the factory. Seemed to cure it.
Also, limp wristing this gun at all will cause FTRB. I could make my XDs .45 do it 3-4 times a magazine by limp wristing the gun. Make sure you are not limp wristing it and causing the failures.
Make sure that the area underneath the extractor hook is clean. If all of this fails to cure the issue, send it back to SA.