[18:53:22 WARN]: [PlaceholderAPI] Plugin PlaceholderAPI v2.8.2 generated an exception while executing task 19
java.lang.IllegalArgumentException: Comparison method violates its general contract!
        at java.util.TimSort.mergeHi(Unknown Source) ~[?:1.8.0_211]
        at java.util.TimSort.mergeAt(Unknown Source) ~[?:1.8.0_211]
        at java.util.TimSort.mergeForceCollapse(Unknown Source) ~[?:1.8.0_211]
        at java.util.TimSort.sort(Unknown Source) ~[?:1.8.0_211]
        at java.util.Arrays.sort(Unknown Source) ~[?:1.8.0_211]
        at java.util.ArrayList.sort(Unknown Source) ~[?:1.8.0_211]
        at java.util.Collections.sort(Unknown Source) ~[?:1.8.0_211]
        at me.clip.placeholderapi.expansion.cloud.ExpansionCloudManager$1.run(ExpansionCloudManager.java:319) ~[?:?]
        at org.bukkit.craftbukkit.v1_12_R1.scheduler.CraftTask.run(CraftTask.java:71) ~[1.12.2.jar:git-Spigot-7754231-94b0980]
        at org.bukkit.craftbukkit.v1_12_R1.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:52) [1.12.2.jar:git-Spigot-7754231-94b0980]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [?:1.8.0_211]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [?:1.8.0_211]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_211]
[19:03:05 INFO]: GroupManager - INFO -  Data files refreshed.

papi 的配置文件中

设置
check_updates: false
cloud_enabled: false
cloud_allow_unverified_expansions: false

之后手动安装扩展即可