May this information are helping for support: This is the full message, which I get…
2019-04-01 08:14:01.070 [ERROR] [nal.common.AbstractInvocationHandler] - An error occurred while calling method 'ThingHandler.handleCommand()' on 'org.openhab.binding.avmfritz.internal.handler.DeviceHandler@16738b4': null
java.lang.NullPointerException: null
at org.openhab.binding.avmfritz.internal.handler.AVMFritzBaseThingHandler.handleCommand(AVMFritzBaseThingHandler.java:190) ~[?:?]
at sun.reflect.GeneratedMethodAccessor121.invoke(Unknown Source) ~[?:?]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
at java.lang.reflect.Method.invoke(Method.java:498) ~[?:?]
at org.eclipse.smarthome.core.internal.common.AbstractInvocationHandler.invokeDirect(AbstractInvocationHandler.java:153) [135:org.openhab.core:2.5.0.201903281407]
at org.eclipse.smarthome.core.internal.common.InvocationHandlerSync.invoke(InvocationHandlerSync.java:59) [135:org.openhab.core:2.5.0.201903281407]
at com.sun.proxy.$Proxy144.handleCommand(Unknown Source) [242:org.openhab.binding.avmfritz:2.5.0.201903310929]
at org.eclipse.smarthome.core.thing.internal.profiles.ProfileCallbackImpl.handleCommand(ProfileCallbackImpl.java:75) [185:org.openhab.core.thing:2.5.0.201903281410]
at org.eclipse.smarthome.core.thing.internal.profiles.SystemDefaultProfile.onCommandFromItem(SystemDefaultProfile.java:49) [185:org.openhab.core.thing:2.5.0.201903281410]
at sun.reflect.GeneratedMethodAccessor120.invoke(Unknown Source) ~[?:?]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
at java.lang.reflect.Method.invoke(Method.java:498) ~[?:?]
at org.eclipse.smarthome.core.internal.common.AbstractInvocationHandler.invokeDirect(AbstractInvocationHandler.java:153) [135:org.openhab.core:2.5.0.201903281407]
at org.eclipse.smarthome.core.internal.common.Invocation.call(Invocation.java:53) [135:org.openhab.core:2.5.0.201903281407]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:?]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:?]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:?]
at java.lang.Thread.run(Thread.java:748) [?:?]
For the moment I tried to install the stable version but this was also not successfull, the snapshot still installed 