Not sure what's the meaning about this. Is there an issue with the communication/encryption to Mojang? Hours before I already had some issues with plugins trying to lookup UUIDs of offline players.
The weird thing here is that it took 12 minutes to run out of memory and shutdown for real.
I know the Spigot build is slightly outdated. The reason for this is that I downgraded from the current build as I could not place (just break) any blocks for unknown reason. But that is a different story.