There almost always is a QB who slides....usually due to a bad Combine or Pro Day.
I can't really see that being Josh.....unless he has accuracy issues. A lot of the Twitter scouts can't stop talking about his completion percentage. A rough day throwing (especially at the Combine) could change the NFL scouting narrative from "teammates can't catch" to "Allen is inaccurate", which could cause him to drop. Guys have dropped in projections from 1st player taken to almost out of the first round entirely between the Combine and draft night, so it could have a major effect.
That's the only potential red flag I see in him or his game.
As for the draft board, this is an interesting free agency year at QB. No true franchise changers likely, but a lot of safer options. Sometimes teams feel better going safe than for major upside, especially if they've been burned or if a staff may be on the hot seat. There's also coaching changes to factor in, which could either open up or close down potential QB picks in the draft.
There are probably four potential spots for a QB in the Top 10. Most expect Cleveland to take one, the Giants likely will, the Broncos might and the Jets might.
Outside of the Top 10, another handful of possibilities between 11 and 20, and another five possible between 21 and 32. But again, obviously not all of those will draft one. I think he'll end up somewhere between 11 and 32. That's actually great news if you want a better situation for Josh. This first contract is peanuts, what is more important is giving him the best opportunity for a second contract (hopefully as a starter). Those teams usually are found the later you get in the round.
Personally, I would love a situation like Jacksonville or Minnesota, both built on great defenses and ball-control offenses, not forcing the QB to do too much. Arizona, Pittsburgh, LA Chargers would allow him to learn behind a veteran until he's ready, while somewhere like Buffalo, Denver or NY Jets could let him make an immediate impact.
Really, I'll be happy for him no matter where he goes! (except Green Bay, that'd be the equivalent of him transferring to CSewe).