I had the same problem with version 2 until I connected my RC receiver and switcht on the RC transmitter. Now everything works fine. Hope I could help you
When unplugged, is your gombal perfectly balanced ?... It has to be. The principle on brushless gimbal is only to tabilise, not to over power... so perfcet balance is necessary prior to power on !
Also, your IMU should be direct to frame, this thick foam could cause echo effect... I put mine in shrink tubing to protect electronics from grounfing to aluminum frame, and then used thin double sided tape. I also placed it under the camera... Hope this helps !