2013 Toyota Avalon - Detached headliner - Where to start?

Sorry you are having this frustrating problem. On the bright side, you aren’t alone. This is a common problem reported here on most cars. I’ve tried the glue it in place method on my Corolla, didn’t last. I’m using a bevy of straight pins ( like what come with a new dress shirt) to hold it up. That’s working pretty good, albeit with some cosmetic compromises.

The proper fix is to remove the entire headliner board from the vehicle, scrape off all the old glue and foam, and attach replacements on the work bench. Besides the difficulty of doing that, there’s the problem of removing the headliner board from the car, which might require removing seats or even one of the windshields. All in all, not easy to fix. Which brings up the question: Why don’t the manufacture’s solve prevent this problem with a robust design? Below is some info on that question …