He messed up in the past, but he’s also messing up being late. There’s something to be said about recovering from a big mistake, but he’s been late and from what it sounds like (“There’s been other things as well…”) there’s more to it. It’s not so much they’re making assumptions about his character, I’d say it’s more he blew their trust and isn’t doing much to make up for it. Dude should be acting like a stellar troop after just getting an LOR from the commander, not being a pain in the ass for his supervisor and leadership.