Multiple Connected BT devices can not be supported (mostly common among iPhones )
For a real time display, GoCube use the BT channel extensively (very frequently transmit the Cube's state and orientation). In case other BT devices are connected, and share the same channel, the normal operation may be Interrupted.
The ways to solve/improve this issue are:
1. If possible, make sure GoCube is the only connected BT device while being used.
2. You can try to turn off the 3D tracking sensor (in the Hamburger menu, on the top left corner of the application), which is less needed/important for most use cases. This will reduce the required bandwidth of GoCube, and will let you play with other BT device in parallel.