[16:38:58 WARN]: [HolographicDisplays] Unable to get a stacktrace element, please inform the developer. You will only see this error once to avoid spam.
java.lang.NoSuchMethodException: java.lang.Throwable.getStackTraceElement(int)
at java.lang.Class.getDeclaredMethod(Class.java:2475) ~[?:?]
at com.gmail.filoghost.holographicdisplays.util.ReflectionUtils.getStackTraceElement(ReflectionUtils.java:44) [HolographicDisplays%20v2.6.6.jar:?]
at com.gmail.filoghost.holographicdisplays.nms.v1_12_R1.EntityNMSArmorStand.getId(EntityNMSArmorStand.java:139) [HolographicDisplays%20v2.6.6.jar:?]
at net.minecraft.server.v1_12_R1.PacketPlayOutEntityTeleport.(SourceFile:22) [spigot-1.12.2.jar:git-Spigot-642f6d2-57ab4cf]
at com.gmail.filoghost.holographicdisplays.nms.v1_12_R1.EntityNMSArmorStand.setLocationNMS(EntityNMSArmorStand.java:202) [HolographicDisplays%20v2.6.6.jar:?]
at com.gmail.filoghost.holographicdisplays.nms.v1_12_R1.NmsManagerImpl.spawnNMSArmorStand(NmsManagerImpl.java:106) [HolographicDisplays%20v2.6.6.jar:?]
at com.gmail.filoghost.holographicdisplays.object.line.CraftTextLine.spawn(CraftTextLine.java:75) [HolographicDisplays%20v2.6.6.jar:?]
at com.gmail.filoghost.holographicdisplays.object.CraftHologram.spawnEntities(CraftHologram.java:300) [HolographicDisplays%20v2.6.6.jar:?]
at com.gmail.filoghost.holographicdisplays.object.CraftHologram.refreshAll(CraftHologram.java:247) [HolographicDisplays%20v2.6.6.jar:?]
at com.gmail.filoghost.holographicdisplays.task.StartupLoadHologramsTask.run(StartupLoadHologramsTask.java:11) [HolographicDisplays%20v2.6.6.jar:?]
at org.bukkit.craftbukkit.v1_12_R1.scheduler.CraftTask.run(CraftTask.java:76) [spigot-1.12.2.jar:git-Spigot-642f6d2-57ab4cf]
at org.bukkit.craftbukkit.v1_12_R1.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:361) [spigot-1.12.2.jar:git-Spigot-642f6d2-57ab4cf]
at net.minecraft.server.v1_12_R1.MinecraftServer.D(MinecraftServer.java:739) [spigot-1.12.2.jar:git-Spigot-642f6d2-57ab4cf]
at net.minecraft.server.v1_12_R1.DedicatedServer.D(DedicatedServer.java:406) [spigot-1.12.2.jar:git-Spigot-642f6d2-57ab4cf]
at net.minecraft.server.v1_12_R1.MinecraftServer.C(MinecraftServer.java:679) [spigot-1.12.2.jar:git-Spigot-642f6d2-57ab4cf]
at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:577) [spigot-1.12.2.jar:git-Spigot-642f6d2-57ab4cf]
at java.lang.Thread.run(Thread.java:834) [?:?]

Please update Holographic Displays to the latest development build, this issue has already been solved.