For what it’s worth, I think you should have gotten a warning on the timing of your break. If you supervisor wants you to take/not take your break at a certain time, they should make a break schedule or tell you when to take or not take your break. For a supervisor to put you on paper out of the blue for taking your break near the end of their shift without having ever told you that it’s unacceptable is harsh. Not too many TMs can read their leaders’ minds, and putting you on a CA Instead of coaching you first for doing something that you don't know is wrong is a double failure of leadership, once for not making you aware of expectations to start with, and once for putting you on a CA for a training issue instead of coaching you.
(ASANTS, but not all leaders/stores give two hoots when TMs take their breaks as long as the workcenter is covered. My store didn’t, except for the front lanes, and they had a break schedule. Every day. For the rest of the store, taking their breaks at the end of their shifts was standard procedure.)
As far as loafing, you got caught, even if it was the first time, it’s still loafing. Bad luck, but not the end of the world, hopefully, unless they truly are picking on you and looking for an excuse to issue a CA. If you get another CA you will know it’s time to start looking for greener pastures.
It’s not worth it to tell leadership about the transgressions of your co-workers, their answer will be that it doesn’t matter what they are doing, you still shouldn’t be loafing. That’s Spot for you, and it’s not fair, but some get away with everything and some get held accountable for the smallest transgression. Good luck!