Could not update selected mods

FAF client gives me the following error when I try to load mods.

java.util.concurrent.CompletionException: java.lang.IllegalStateException: java.lang.IllegalStateException: Duplicate key 4c6694bd-aaaa-aa12-8fe7-cf2c9e8e8889 (attempted merging values true and true)
at org.springframework.aop.interceptor.AsyncExecutionAspectSupport.lambda$doSubmit$3(AsyncExecutionAspectSupport.java:279)
at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1764)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
at java.base/java.lang.Thread.run(Thread.java:832)
Caused by: java.lang.IllegalStateException: java.lang.IllegalStateException: Duplicate key 4c6694bd-aaaa-aa12-8fe7-cf2c9e8e8889 (attempted merging values true and true)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:64)
at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
at java.base/java.util.concurrent.ForkJoinTask.getThrowableException(ForkJoinTask.java:600)
at java.base/java.util.concurrent.ForkJoinTask.reportException(ForkJoinTask.java:678)
at java.base/java.util.concurrent.ForkJoinTask.invoke(ForkJoinTask.java:737)
at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateParallel(ReduceOps.java:919)
at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:233)
at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:578)
at com.faforever.client.mod.ModService.overrideActivatedMods(ModService.java:315)
at com.faforever.client.mod.ModService.updateAndActivateModVersions(ModService.java:437)
at com.faforever.client.mod.ModService$$FastClassBySpringCGLIB$$aae9cfd3.invoke(<generated>)
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:779)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:750)
at org.springframework.aop.interceptor.AsyncExecutionInterceptor.lambda$invoke$0(AsyncExecutionInterceptor.java:115)
at org.springframework.aop.interceptor.AsyncExecutionAspectSupport.lambda$doSubmit$3(AsyncExecutionAspectSupport.java:276)
... 4 more
Caused by: java.lang.IllegalStateException: Duplicate key 4c6694bd-aaaa-aa12-8fe7-cf2c9e8e8889 (attempted merging values true and true)
at java.base/java.util.stream.Collectors.duplicateKeyException(Collectors.java:133)
at java.base/java.util.stream.Collectors.lambda$uniqKeysMapMerger$0(Collectors.java:155)
at java.base/java.util.stream.ReduceOps$3ReducingSink.combine(ReduceOps.java:174)
at java.base/java.util.stream.ReduceOps$3ReducingSink.combine(ReduceOps.java:160)
at java.base/java.util.stream.ReduceOps$ReduceTask.onCompletion(ReduceOps.java:959)
at java.base/java.util.concurrent.CountedCompleter.tryComplete(CountedCompleter.java:592)
at java.base/java.util.stream.AbstractTask.compute(AbstractTask.java:328)
at java.base/java.util.concurrent.CountedCompleter.exec(CountedCompleter.java:746)
at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290)
at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1016)
at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1665)
at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1598)
at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:183)

Does anyone have an idea what may cause this? It says something about permissions ... do I have to start it as admin?

It is complaining because it seems like you have two mods with identical uuids. So make sure you don't have the same mod in two different folders

@sheikah Hi, thanks for the answer! That is probably because I was trying to make a mod myself and it doesn't have a UID since I don't know what is needed in that field. Do you happen to know where I could read up on that?

It's just a random number to have a way to uniquely identify each mod. You can use a site like this to generate one: https://www.uuidgenerator.net/

@blackyps got it! Thanks a lot