I think FB had a major issue on mobile (and PC), related to touchscreen management and RS1. Much more visible on mobile of course, the issue was that at some time, the touchscreen would turn irresponsive, the app would continune to update but without the possibility to interact as touchscreen was disabled. And when this happened in one of the 3 FB apps (Messenger, Instagram, Facebook), the three of them would be stuck in that state. Instagram doesn't react to touch, then it's the same in FB and Messenger, and only a reboot will fix it.
I've been told the same issue occured on PC too, but as people would use keyboard and mouse most of the time, they wouldn't realise.
My guess so far was that it's a OSMeta/Windows 10 issue.
BUT. Since the last instagram updates (last week), when FB is irresponsive, then Messenger is irresponsive too but not Instagram. Instagram continues to work.
I presume they've fixed that Osmeta bug, at least for Instagram. I expect a FB/Messenger update on mobile soon to bring that Osmeta fix to all of FB apps.
I second this. This is exactly what's been happening to me, except that it ALWAYS starts with FB being unresponsive, triggering a chain reaction which causes both IG and Messenger to become unresponsive as well.
Although Instagram is the better app of the bunch, I'm still disappointed that the latest update has not yet fixed the annoying crash from pressing the Windows back button during certain operation in IG, which are:
1) Open Insta Stories (doesn't matter if it's your friend's or from the Search tab, as long as it's IG stories) and, while viewing it, press the WINDOWS back button (not the X button at the top right). From here, you'd expect the stories to close, and you'd be back either on your home page or at the Search page, but instead IG will crash/force close.
2) Opening a photo via "3D touch" (hold at thumbnail, swipe up to reveal Like, Share, etc.), and pressing the back button (Windows back button, not the iPhone-isque back button on the top left), you'd expect for the photo preview to close and you'll return to the grid view of your Home or Search tab. Alas, IG crashes.
Although, I must say that as of now, (1) is still occurring on my Lumia 950, while (2) is somewhat fixed. It still happens, but very, VERY rarely.
Hoping IG, as well as the other two FB apps be more optimized in the future for W10M.