Rise courses disappear from Rise 360 folders and reappear on level All Content

Hello all, 

I have an annoying problem with the folders in Rise 360. As seen on screenshot 1, I keep my courses/learning-steps under course folders. Currently I'm working on the course/project "Willkommen bei EM Logistik" (one folder).

This course has currently 10 learning-steps, but whenever and however I move certain steps into this folder, they keep disapparing from the folders and seem to fall back onto level All-Content (as seen in Screenshot 2, step AS/GS für Fahrer, who I had moved to it's folder but when I come back I only find it here.  

The really anoying part is, when I then try to move it back to the folder. Cause it doesn't let me, since the steps seems to be part of the folder already (screenshot 3). But why doesn't it show? at the moment I do the workaround to move the step to another folder and then move it back to folder "Willkommen bei EM Logistik". But each time I reenter Rise 360, this folder only shows 8 steps, instead of 10.  

Is this behaviour known or am I the only one being hindered by this? 

Thx in advance for your hints and best regards
Roland