I thought I remembered seeing somebody here having a problem with this.
Here's the solution, from Avid MC3 Release Notes:
The JVC GY-HD250U camera might drift out of sync while shooting in 720p/59.94. To avoid this issue, turn on the camera in 720p 23.976 and then switch the format to 720p 59.94 causing a soft reboot.
Here's the solution, from Avid MC3 Release Notes:
The JVC GY-HD250U camera might drift out of sync while shooting in 720p/59.94. To avoid this issue, turn on the camera in 720p 23.976 and then switch the format to 720p 59.94 causing a soft reboot.