Why does my FR 945 suddenly stop tracking while running?

Hi, guys 

I'm so curious about if the issue I sometimes faced to is being occured to other FR 945 owners.

I'm still really satisfied with my Forerunner 945 since I had it 3 years ago. However, I noticed it suddenly stops tracking running and back to the original FR 945 default watch face(the image attached below). I'm using the running data field named "F3b Dozen Run" from IQ store and I really like this one to track my running habbits. 

I don't doubt if the issue has been happening occasionally becaue of the running data.  When my watch stops tracking and back to the original FR 945 watch face, after I start run for 5~6 min. As I said before it actually happens not quite often, but I'm still being interrupted whenever it happens and I find out checking my pace. In addition, I press Start/Stop botton as soon as I saw and realized that my watch stopped tracking and it continued to re-track all the informaion, such as GPS, Pace, Heartneat and others supplied by the data I used for running. Have any body had the exact issue ever before ? 

How can I make the issue stop being happening?