Iisshaub: "This was bugging me with my 5s on iOS 7 and it's still here on my 6+ on iOS 9. Turning off in app sounds and autoplay videos helped but it still happens occasionally."
Grimmac: "Unfortunately I don't think is a bug. I think they are trying to be smart and "best" set the volume, also infuriates me."
Facebook's iOS apps aren't worth installing, just login to the service in Safari. You'll save storage space and you can send messages without needing the Messenger app.
I noticed a similar problem on my iPhone 6 Plus, but I had no idea what was going on until I saw that thread on Reddit. I suspect many other iPhone users have probably encountered it as well. Facebook hasn't been particularly helpful in trying to fix it either.
Skip Facebook's iOS apps and just use it in Safari
The easiest way around the problems of the Facebook apps is to skip installing them on your iOS devices. If you want to use Facebook, just login via Safari on your iPad, iPhone or iPod touch. Facebook works perfectly in Safari, and you have the added benefit of being able to send and receive messages the usual way instead of having to fiddle with Messenger.
And if you skip installing the two Facebook apps you can also save around 250MB of space on your iOS device. That's not a huge amount of space, but every little bit helps, particularly if you have an iOS device with a limited amount of storage.
Another benefit of using Facebook in Safari in iOS is the ad blockers that will become available in iOS 9. You cannot block ads in Facebook's iOS apps, but you will be able to block them on Facebook's site in Safari. This is going to be a huge advantage for the folks that tire of seeing Facebook's advertising while using the service.
So if you use Facebook on an iOS device, skip the company's apps and use Facebook in Safari. You'll be very glad you did.
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