There is no v3.5.3 image.
If you’re on v3.4.0 please install this hotfix that I have announced long time ago in the main rooExtend Support Thread.
After that, the nightly update will update your rooExtend to v3.5.3 
Best DrCWO
Thx, will do! 
At the moment 3.4.0 just works fine.
I can see it in the about section and I see the Roon bridge and after some hassle with my Genelecs music is also back.
Hmm, with my RPi3 in my bed room (connected via LAN) I do not get a continous streaming…
I have now always only a play time for a couple of seconds and than a way longer break of several seconds…
Even with a low quality 128 kps mp3 radio stream.
Not sure if this has anyting todo with rooExtend but with the old rooExtend version everything worked fine. 
(RPi4 works fine, RPi3 already underpowered?)