The user guide states E27 Bridge Hardware Fault is caused by Excessive current or short on the H-bridge. This isn't a common fault but for further details in troubleshooting this error:
This fault typically indicates a short circuit in the motor or motor power cable. If power can be cycled to the drive and the bit clears (following removal of the motor power cable from the drive), then odds are that the drive has not suffered permanent damage. However, this bit can also be triggered by a physical failure of the bridge rectifier within the drive. Bridge over-current or a voltage spike can cause damage of this severity. If the fault is caused by a physical failure, the bit will not clear under any circumstances, and will remain active after cycling drive power. In this case, the unit will need to be sent in for repair or component replacement.
If this bit is always active regardless of what you do, then the drive is most likely damaged and needs to be repaired.
If this bit only goes active when the drive is enabled, and can be cleared by either...
A) disabling and re-enabling the drive, or by
B) cycling power,
...check the motor's power wiring to the drive. Then confirm that the proper motor configuration file has been downloaded into the drive.
If this bit only occasionally goes active, then there are two likely causes with a third cause that is rather unlikely:
1) An intermittent short in the motor or motor cable. The only way to find this is by swapping out one component at a time until you are confident that the failure has gone away.
2) Electrical noise causing voltage spikes at the sensor inside of the drive can cause the drive to register this fault. Compare the installation to the EMC Installation guidelines in the Hardware Installation Guide. Make sure that the motor cable's shielding is properly connected at both the drive and motor ends of the cable.
3) The Current Loop that controls the current going to the motor becomes unstable and spikes the drive with current. This can occur with motors that have really low inductance. Certain motor designs, like Parker's BE16, can also cause it because the inductance significantly drops during operating of the motor as it heats up. Sudden motor jams also can cause the current to spike. Reduce the current loop gain (DIBW) to reduce the responsiveness of the Current Loop. This will reduce the current overshoot and prevent motor&drive overheating.
Drive current foldback (DIFOLD1) can be enabled that will fold the drive's continuous current output to 80%, reducing current (reduces motor torque and thus may cause servo tracking errors at higher accelerations/decelerations) and thus reduces motor/drive heating. This doesn't reduce peak current until after the overcurrent occurs, (see DIFOLD command in user guide for graph that shows the time for overcurrent) Example: 3.375sec for the AR-04 (at 9Arms).
Note an undertuned servo drive/motor/controller also causes position overshoot and ringing and the current would also be overshooting. Properly tuning the motor/drive will reduce overshoot and motor heating.
Electronics are warrantied for 2 years and depending upon how often these are used, could be standard wear. If the drive's current rating is less than the motor's current rating, it can cause the drive to operate in the peak current region more often and cause the bridge to wear faster than a larger amplifier. Consider reviewing the motor sizing and the operating currents during normal operation to confirm the proper amplifier size.