Upon loading up my 1.18.1 modpack, I get a ClassNotFoundException. I am running forge version 39.1.2 and Placebo version 6.1.1. I'll attach my full latest.log , but here's the snippet with the Exception:

[11:37:42] [modloading-worker-0/FATAL]: Failed to load mod class Lshadows/placebo/util/PlaceboTaskQueue; for @EventBusSubscriber annotation
java.lang.ClassNotFoundException: shadows.placebo.util.PlaceboTaskQueue
at cpw.mods.cl.ModuleClassLoader.loadClass(ModuleClassLoader.java:138) ~[securejarhandler-1.0.3.jar:?]
at java.lang.ClassLoader.loadClass(ClassLoader.java:520) ~[?:?]
at java.lang.Class.forName0(Native Method) ~[?:?]
at java.lang.Class.forName(Class.java:467) ~[?:?]
at net.minecraftforge.fml.javafmlmod.AutomaticEventSubscriber.lambda$inject$6(AutomaticEventSubscriber.java:75) ~[javafmllanguage-1.18.1-39.1.2.jar%23170!/:?]
at java.util.ArrayList.forEach(ArrayList.java:1511) ~[?:?]
at net.minecraftforge.fml.javafmlmod.AutomaticEventSubscriber.inject(AutomaticEventSubscriber.java:62) ~[javafmllanguage-1.18.1-39.1.2.jar%23170!/:?]
at net.minecraftforge.fml.javafmlmod.FMLModContainer.constructMod(FMLModContainer.java:91) ~[javafmllanguage-1.18.1-39.1.2.jar%23170!/:?]
at net.minecraftforge.fml.ModContainer.lambda$buildTransitionHandler$4(ModContainer.java:120) ~[fmlcore-1.18.1-39.1.2.jar%23169!/:?]
at java.util.concurrent.CompletableFuture$AsyncRun.run(CompletableFuture.java:1804) [?:?]
at java.util.concurrent.CompletableFuture$AsyncRun.exec(CompletableFuture.java:1796) [?:?]
at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:373) [?:?]
at java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1182) [?:?]
at java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1655) [?:?]
at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1622) [?:?]
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:165) [?:?]
[11:37:42] [modloading-worker-0/ERROR]: Failed to register automatic subscribers. ModID: placebo, class shadows.placebo.Placebo
java.lang.RuntimeException: java.lang.ClassNotFoundException: shadows.placebo.util.PlaceboTaskQueue
at net.minecraftforge.fml.javafmlmod.AutomaticEventSubscriber.lambda$inject$6(AutomaticEventSubscriber.java:80) ~[javafmllanguage-1.18.1-39.1.2.jar%23170!/:?]
at java.util.ArrayList.forEach(ArrayList.java:1511) ~[?:?]
at net.minecraftforge.fml.javafmlmod.AutomaticEventSubscriber.inject(AutomaticEventSubscriber.java:62) ~[javafmllanguage-1.18.1-39.1.2.jar%23170!/:?]
at net.minecraftforge.fml.javafmlmod.FMLModContainer.constructMod(FMLModContainer.java:91) ~[javafmllanguage-1.18.1-39.1.2.jar%23170!/:?]
at net.minecraftforge.fml.ModContainer.lambda$buildTransitionHandler$4(ModContainer.java:120) ~[fmlcore-1.18.1-39.1.2.jar%23169!/:?]
at java.util.concurrent.CompletableFuture$AsyncRun.run(CompletableFuture.java:1804) [?:?]
at java.util.concurrent.CompletableFuture$AsyncRun.exec(CompletableFuture.java:1796) [?:?]
at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:373) [?:?]
at java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1182) [?:?]
at java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1655) [?:?]
at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1622) [?:?]
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:165) [?:?]
Caused by: java.lang.ClassNotFoundException: shadows.placebo.util.PlaceboTaskQueue
at cpw.mods.cl.ModuleClassLoader.loadClass(ModuleClassLoader.java:138) ~[securejarhandler-1.0.3.jar:?]
at java.lang.ClassLoader.loadClass(ClassLoader.java:520) ~[?:?]
at java.lang.Class.forName0(Native Method) ~[?:?]
at java.lang.Class.forName(Class.java:467) ~[?:?]
at net.minecraftforge.fml.javafmlmod.AutomaticEventSubscriber.lambda$inject$6(AutomaticEventSubscriber.java:75) ~[javafmllanguage-1.18.1-39.1.2.jar%23170!/:?]
... 11 more

latest.log

You have two placebo jar files installed.