There is no end to the issues users encounter with Facebook's suite of apps for Windows 10 Mobile, such as 'big blue' itself, Messenger and Instagram. The apps have been ported to Windows 10 Mobile by using Facebooks OSMeta technology, which allows iOS's Objective-C to execute on other platforms.
Facebook recently set a "Minimum requirement" for the available system RAM memory for its app on Windows 10 Mobile. The store page now shows that you need 2GB of RAM for the apps to run properly.
The new requirement doesn't mean that phones with 1GB or 512MB of RAM won't be able to install it. It just means that these phones aren't officially supported, and there might be problems that may occur only on those devices. MSMobile was able to get the apps to install on a Microsoft Lumia 650, even though it has only 1GB of RAM, and WinBeta confirmed this by testing the same apps on the same device, as well as a Microsoft Lumia 640.
We also tested Instagram and checked it's requirements but it does not list anything for the Minimum Requirements, and it installed and worked perfectly fine as well.
This may not seem like a big deal, but keep in mind that the Facebook and Messenger apps now are only officially supported on flagship devices like the HP Elite x3, Lumia 950, Acer Jade Primo and a few others. This might mean that low-end Lumia model user may never see a well working Facebook app on their phone moving forward.