The Framework 16 had an issue where the closed lid would flex slightly in your backpack, and press keys on the keyboard, waking up the computer. Ten days ago (Nov 14th), Framework released a BIOS update for the 16 that would turn off the keyboard (and numeric pad) when the lid was closed. I installed that update
immediately, and for the first time, when I pulled my laptop out of my backpack after leaving the office and going home (or the reverse), it was still suspended. Had nothing to do with Windows drivers (I run Linux on this laptop), was purely a physical issue.
I haven't checked if the Framework 13 got BIOS updates at the same time. But you could check if the keyboard is causing the wakeup (the Framework 13 has the same keyboard as the 16, but its smaller screen means less flexing in a backpack so it might not be suffering the same issue) by opening a Notepad window before putting the computer to sleep and closing the lid. If you find that random characters have been typed into Notepad while it's sleeping, then the issue was the same that the 16 was experiencing: the keyboard needs to be disabled while the lid is closed. If you don't see random typing with the lid closed, then it's a different issue.