I bought a DVC 3-gun, new, around Christmas 2018. I have 7 of the newer STI magazines. I have never used spacers, and I've never had a problem with the magazines. I've shot everything from WWB to my own long reloads, no problems at all. I'm guessing the guy who sold this to you kept the newer magazines and dumped these on you, since you didn't know better. I'd suggest you get new STI mags and put these away.