Xrdp login with domain account

Dear all! After many tries and errors I’ve implemented successfully a domain network based on Raspberry 3 with Ubuntu mate 16.0x . Logins with Windows clients work perfectly. Also logins with Ubuntu clients by SSH work without problems. The only thing which is still not work properly is the login with a domain account via xrpd. The strange thing is that always the first login attemp fails. The second attemp then works. I have asked uncle Google, read manuels and tried with some things with the configuration. Everything without success, the problem persists. It is not a big problem - I know. But I’d be interested in the solution anyway. If further information is needed from my side I’d be glad to answer. I appreciate any suggestions and support. With my best regards fox123