xrdp configured, connects successful then terminates

xrdp is setup, connections to client work: mstsc connects to client, authentication is successful, then starts x11, starts session, terminates session, terminates x11, closes connection. All without any visible error. Any idea why?

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: xrdp 0.9.12-1
ProcVersionSignature: Ubuntu 5.4.0-33.37-generic 5.4.34
Uname: Linux 5.4.0-33-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.2
Architecture: amd64
CasperMD5CheckResult: skip
Date: Sat Jun 6 23:33:49 2020
InstallationDate: Installed on 2019-09-09 (271 days ago)
InstallationMedia: Xubuntu 19.04 "Disco Dingo" - Release amd64 (20190416)
ProcEnviron:
 LANGUAGE=de_DE
 TERM=screen
 PATH=(custom, no user)
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: xrdp
UpgradeStatus: No upgrade log present (probably fresh install)