So this issue has been going on for the past week, and there doesn't seem to be an end. We're pretty confident it is a ProtoclLib issue.

We are seeing the same error show only for plugins that use ProtocolLib, here is an example:

[18:12:30 WARN]: [Coinflip] Task #9922795 for Coinflip v1.0 generated an exception
net.minecraft.server.CancelledPacketHandleException: null

It's really hurting us as a server, and many of our plugins rely on this one in order to function.

Please append the full stack trace, as well as the protocollib dump in order for us to help you