If CallInterceptor.handleDefault(...) is called with a RemoteTxInvocationContext, and if command invocation throws an exception, the catch clause ends up hiding this with an IllegalStateException.
The culprit is RemoteTxInvocationContext.isValidRunningTx(), which internally calls RemoteTxInvocationContext.getRunningTransaction(), which always throws an ISE.
If this method would instead return null, RemoteTxInvocationContext.isValidRunningTx() will return false, and all is well, and the genuine exception can propagate properly.