After 5 - 15 minutes connected to my Realm, I am getting kicked with several different messages, all beginning with Internal Exception:io.netty.handler.codec.DecoderException:" and then continuing with a variety of different messages.
Problem does not occur on singleplayer. I have tried the following: setting render distance to minimum, lowering graphics settings, leaving and rejoining the Realm, fresh installation of the game, restarting my computer, setting my DNS server to Google's, checking for driver updates on my network adapter.
I have seen reports of this error happening with extremely data-heavy chunks (large libraries, for example). This situation does not exist in my Realm.
This appears to be a duplicate of REALMS-1656, which hasn't yet been resolved. If you have any additional information to provide regarding this issue, feel free to comment on the parent ticket. If you feel that this issue is affecting you, feel free to vote for the duplicated ticket, to give Mojang a basic idea of how many people are impacted by the problem. Just to further inform you, this will not determine how quickly the bug gets handled or fixed.