@sheikah I deleted the folder with Gas Powered Games - the problem disappeared. Thanks.

When the antivirus is turned off, the same problem occurs.

I deleted all the mods.

java.util.concurrent.CompletionException: java.lang.reflect.UndeclaredThrowableException
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$Worker.run(ThreadPoolExecutor.java:630)
at java.base/java.lang.Thread.run(Thread.java:832)
Caused by: java.lang.reflect.UndeclaredThrowableException
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:759)
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.nio.file.AccessDeniedException: C:\Users\User\AppData\Local\Gas Powered Games\Supreme Commander Forged Alliance\Game.prefs
at java.base/sun.nio.fs.WindowsException.translateToIOException(WindowsException.java:89)
at java.base/sun.nio.fs.WindowsException.rethrowAsIOException(WindowsException.java:103)
at java.base/sun.nio.fs.WindowsException.rethrowAsIOException(WindowsException.java:108)
at java.base/sun.nio.fs.WindowsFileSystemProvider.newByteChannel(WindowsFileSystemProvider.java:235)
at java.base/java.nio.file.spi.FileSystemProvider.newOutputStream(FileSystemProvider.java:478)
at java.base/java.nio.file.Files.newOutputStream(Files.java:224)
at java.base/java.nio.file.Files.write(Files.java:3491)
at java.base/java.nio.file.Files.writeString(Files.java:3707)
at com.faforever.client.mod.ModService.writeModStates(ModService.java:420)
at com.faforever.client.mod.ModService.overrideActivatedMods(ModService.java:364)
at com.faforever.client.mod.ModService.updateAndActivateModVersions(ModService.java:483)
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$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:771)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:749)
... 6 more

Were you able to solve the problem?