SSM2019 fails with high input current

We are using SSM2019 for balanced MIC pre-amp. It is powered by +/- 15v source.

Occassionaly a device fails in operation with no apparent reason. When testing failed device with multi-meter it looks like the input stage broke but I can't be sure on that.

The design include schottky diodes (BAR43CFILM) for clamping the input signals. In addition the microphone input connector has ESD protection diodes (TPD2E007).

Any ideas?

Thanks,

David