Server console output: https://pastebin.com/raw/NhUvSLdv

Build #86 from https://ci.codemc.org/job/filoghost/job/HolographicDisplays/
[17:51:14] [Server thread/INFO]: [HolographicDisplays] Enabling HolographicDisplays v2.3.3-SNAPSHOT
[17:51:14] [Server thread/INFO]: [HolographicDisplays] Enabled player relative placeholders with ProtocolLib.
08.08 17:56:30 [Server] Server thread/INFO This server is running CraftBukkit version git-Spigot-cbcc8e8-06efc9e (MC: 1.14.4) (Implementing API version 1.14.4-R0.1-SNAPSHOT)
ProtocolLib v4.4 build #14

edit: After updating ProtocolLib (v4.5.0; build 16) those errors seems to be gone.
http://ci.dmulloy2.net/job/ProtocolLib%20Gradle/lastStableBuild/