We've had a similar intermittent problem with the Trimble R1 and the Collector app on an iPad Mini 3. In this case, the map is used offline, and the Trimble R1 is connected to SBAS for corrections. The iPad is allowed to go into sleep mode in between different points of feature collection.
However, I have not noticed any similar issue with the Trimble R2 and the Collector app on an iPad Mini 1. In this case, the map is live and is accessed with a wifi unit, and the Trimble R2 is connected to a local RTK network for corrections. The iPad is typically not allowed to go to sleep in between different points of feature collection.
It's on my to-do list to investigate more and/or contact Esri support.