Is it possible to appear offline on Facebook through mobile or messenger and have your last active time reset?

[Sanity Not Included]

I've heard that the last active time stamp on Facebook is completely accurate, but I've also heard there are bugs that reset the last active time stamp for whatever reason. I want to know if it's possible for someone on your chat bar to appear offline through messenger app or mobile (ex. "9m" next to cell phone icon on the chat) and begin retaining a last active time and then suddenly resetting back to "1m" without appearing online (green dot) and remaining "offline". If so, does that mean the user has been replying to messages? Or is that even possible? Or what exactly is it? I've been seeing this happen with someone on my friends list and I'm very curious about it, it's strange.
Or, what does it mean when the last active time stamp on facebook chat goes from "9m" to "1m" without the green dot showing up for a contact