I had the same problem. Sometimes it took longer, sometimes less until the live image froze (but it usually stopped at about 30 seconds). When the problem occurred, the camera no longer reacted (the gimbal then remained in the same place and no longer moved). At that time I had tried the following as suggested by the DJI support site:
1. formatted the SD card
2. reset the DJ Osmo to factory settings
3. other video settings (Full HD, 4K, lower quality)
4. other SD card
5. test without accessories connected (control wheel, radio module)
6. reinstalled the Mimo app
But the problem still occurred. I sent the camera back to Digitec and received the repaired version. No more problems since then.