DCC Loco erratic behavior on DC

Hello all,

I very recently purchased my first DCC locomotive. It's an Athearn Genesis SD70MAC (ATHG64895) with DCC/Sound. I've also ordered a DCC system on Sunday to go with it, but it has not yet arrived. I decided to try it out on my DC layout, as it's allegedly supposed to work on DC.

Thing is, sometimes it works, sometimes it doesn't. There will be periods of time when it works perfectly, then there will also be periods of time where I cannot get it to function correctly. What it will do is cut out every two seconds. Run for 2 seconds, cut off for 2 seconds, run for 2 seconds, cut off for 2 seconds, etc. I know it's not any kind of overheating issue because it will behave erratically even if I just turned the system on. I've tried everything I can think of. Completely different power packs, different wall outlets, letting it idle for a while before moving, you name it. I scoured Google, but I think that maybe I'm not searching for the right terms as I can't find anything related to my issue.

If it's just an issue with using DCC on DC, fine. I'm just concerned that there is something wrong with the decoder. While I don't have plans to ever run it on DC once my DCC setup is in play, I spent a lot of money on this loco and if it's supposed to work properly I want to know that it's not broken while it's still under warranty. Any thoughts?