Magenta & black blocks appearing & having to redownload realm data

Every few times I enter a friend's realm, I have to redownload the data. Sometimes it only makes me redownload some of the data, and that's when I get magenta & black blacks. For example, if my friend's realm has add-on/data that is 120mb, if when entering the realm, if tells me I need to download 60mb, I know for certain objects/textures will be the magenta blocks. The only fix I found is to delete all the data on the app and redownload it, which is of course tedious and annoying.