This get thrown at server ini:

[20:54:08 ERROR]: Error occurred while enabling Stargate v0.10.5.2 (Is it up to date?)
java.lang.NoClassDefFoundError: java/lang/constant/Constable
at net.TheDgtl.Stargate.Stargate.loadAllPortals(Stargate.java:246) ~[?:?]
at net.TheDgtl.Stargate.Stargate.onEnable(Stargate.java:165) ~[?:?]
at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:263) ~[patched_1.16.5.jar:git-Paper-468]
at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:380) ~[patched_1.16.5.jar:git-Paper-468]
at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:483) ~[patched_1.16.5.jar:git-Paper-468]
at org.bukkit.craftbukkit.v1_16_R3.CraftServer.enablePlugin(CraftServer.java:500) ~[patched_1.16.5.jar:git-Paper-468]
at org.bukkit.craftbukkit.v1_16_R3.CraftServer.enablePlugins(CraftServer.java:414) ~[patched_1.16.5.jar:git-Paper-468]
at net.minecraft.server.v1_16_R3.MinecraftServer.loadWorld(MinecraftServer.java:465) ~[patched_1.16.5.jar:git-Paper-468]
at net.minecraft.server.v1_16_R3.DedicatedServer.init(DedicatedServer.java:239) ~[patched_1.16.5.jar:git-Paper-468]
at net.minecraft.server.v1_16_R3.MinecraftServer.w(MinecraftServer.java:936) ~[patched_1.16.5.jar:git-Paper-468] at net.minecraft.server.v1_16_R3.MinecraftServer.lambda$a$0(MinecraftServer.java:174) ~[patched_1.16.5.jar:git-Paper-468]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_281]
Caused by: java.lang.ClassNotFoundException: java.lang.constant.Constable
at java.net.URLClassLoader.findClass(Unknown Source) ~[?:1.8.0_281]
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:182) ~[patched_1.16.5.jar:git-Paper-468]
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:111) ~[patched_1.16.5.jar:git-Paper-468]
at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_281]
at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_281]
... 12 more

How to recreate (might only be a thing from my setup): Compile the plugin, check if it works, if not, recompile it (redo this untill you get an error). Cleaning the target folder has always solved this issue for me, but that might be affirmative bias

No-one is really affected by this except for developers, as the plugin file works completely fine once it has been compiled properly. (extremely low priority)

Has not reoccurred