Is this really related to MCPE-32501 though? The issues are slightly different as this one relates specifically to downloading your realm, not ongoing game play where it complains about running out of memory.
I also continue to have this issue on iOS 12.1.4 with Minecraft 1.10. This issue persists on 4 different iOS devices, 2 iPads and 2 iPhones all with a significant amount of free space.
Just attached an example screenshot of the error