Rough English translation of the above post
MoodleBox can not handle more than 17-19 users at the same time.
I use another router - specifically a RAVPower Filehub AC750 (model: RP-WD009). You can configure the device to connect to the WLAN of the MoodleBox (WLAN mesh). This allows groups of more than 25 people to access the MoodleBox without any problems.
Either way, the RAVPower is such an extremely useful device that it is worth the purchase :-)