Dekko 2 - no sync of messages

vmbonn

Nexus 4
Dekko 2 Version 0.1.5
OS-Build-Number r2
Ubuntu-Build 15.04 - armf (20171218)

I've installed Dekko 2 Version 0.1.5 and connected to an IMAP server.
After an initial sync of the inbox no more refreshed occured.

I switched over to dekko.dekkoproject_0.9.4_armhf.click and (most) of the functionality works fine.

What's wrong with Dekko 2 ?

Greetings

Michael