Important, as described here https://bugs.mojang.com/browse/MC-118733

Apparently Solved with Netty 4.1.10 (currently 4.1.9?)
https://github.com/netty/netty/issues/6607

Server is crashing every hour.

[10:28:49] Netty Server IO #0/WARN: Failed to re-register a Channel to the new Selector.
java.lang.ClassCastException: io.netty.channel.nio.SelectedSelectionKeySetSelector cannot be cast to java.nio.channels.spi.AbstractSelector
at java.nio.channels.spi.AbstractSelectableChannel.register(Unknown Source) ~[?:1.8.0_131]
at io.netty.channel.nio.NioEventLoop.rebuildSelector0(NioEventLoop.java:347) [spigot-1.12.jar:git-Spigot-cd6ba67-a7d074c]
at io.netty.channel.nio.NioEventLoop.rebuildSelector(NioEventLoop.java:318) [spigot-1.12.jar:git-Spigot-cd6ba67-a7d074c]
at io.netty.channel.nio.NioEventLoop.select(NioEventLoop.java:769) [spigot-1.12.jar:git-Spigot-cd6ba67-a7d074c]
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:388) [spigot-1.12.jar:git-Spigot-cd6ba67-a7d074c]
at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:858) [spigot-1.12.jar:git-Spigot-cd6ba67-a7d074c]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_131]