Paper stuck in “ASAP” status: what does it indicate? I am looking at a paper by some colleagues, that has been in ASAP status for 4 months now. In that particular journal, “ASAP” indicates accepted papers after the authors have corrected the proofs: i.e., they are just like the final paper, except they have not been attributed an issue and page number yet (and have thus not yet appeared in print).

Most papers in that particular journal only stay 2 or 3 weeks in ASAP status, before being assigned an to an issue. This paper stands out, being the only one so old on the website. Yet, no indication additional information is given on the publisher's website.

What can cause a paper to be stuck so long in ASAP queue? Would it be impolite to ask the corresponding author what's going on? (I admit it would only be to satisfy my own curiosity…)
As was mentioned in the comments, one possibility is that the editors are waiting for a better time to publish the paper, perhaps as part of a special issue or to highlight the paper on its cover.

Another possibility is that the authors have not fulfilled some requirements for publication like signing a copyright transfer form or paying the page charges.

Or perhaps there are some problematic issues about the paper.  Maybe the topic is controversial and some members of the board don't want it published, or perhaps the editors suspect some unethical publication practice.  (If it is this last reason, then perhaps it would be impolite to ask the authors about it.)