I have removed all mods and when trying to create a game I get this:

java.util.concurrent.CompletionException: NotifiableException(i18nKey=mod.errorUpdatingMods, i18nArgs=[])
at org.springframework.aop.interceptor.AsyncExecutionAspectSupport.lambda$doSubmit$3(AsyncExecutionAspectSupport.java:281)
at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1768)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
at java.base/java.lang.Thread.run(Thread.java:833)
Caused by: NotifiableException(i18nKey=mod.errorUpdatingMods, i18nArgs=[])
at com.faforever.client.mod.ModService.writeModStates(ModService.java:371)
at com.faforever.client.mod.ModService.overrideActivatedMods(ModService.java:312)
at com.faforever.client.mod.ModService.updateAndActivateModVersions(ModService.java:433)
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$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:793)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:763)
at org.springframework.aop.interceptor.AsyncExecutionInterceptor.lambda$invoke$0(AsyncExecutionInterceptor.java:115)
at org.springframework.aop.interceptor.AsyncExecutionAspectSupport.lambda$doSubmit$3(AsyncExecutionAspectSupport.java:278)
... 4 more
Caused by: java.nio.charset.MalformedInputException: Input length = 1
at java.base/java.lang.String.throwMalformed(String.java:1240)
at java.base/java.lang.String.throwMalformed(String.java:1246)
at java.base/java.lang.String.newStringNoRepl1(String.java:769)
at java.base/java.lang.String.newStringNoRepl(String.java:738)
at java.base/java.lang.System$2.newStringNoRepl(System.java:2390)
at java.base/java.nio.file.Files.readString(Files.java:3369)
at com.faforever.client.mod.ModService.writeModStates(ModService.java:337)
... 13 more

As far as I can see, nothing is being created in the themes folder. To fix this, the client reinstalled with the complete removal of configs and even changed the security policy for the folder C:\ProgramData\FAForever\themes full access for everyone. None of this helped.
The problem itself has arisen quite recently, about a week at most.

Same problem. Reinstall doesn't help