I am having the same issue when trying to update the software from 4.8.0.to 4.9.4.
I tried using both a Samsung S7 and a Samsung S4 using the latest Estimote app, the upgrade starts, then sticks on 10%, then I receive the error:
Beacon update failed: com.estimote.sdk.exception.EstimoteException: DFU gatt error 133
The beacon has Hardware Revision G1.8.
I was able to successfully update my two other beacons that had a newer software than 4.8.0. (I think they had 4.9.1.)
Would appreciate any help in solving this error.