AD8293G160 EMC Considerations

We use the AD8293G160 to amplify a strain gauge that measures water pressure in a household or commercial environment.  It's a product that has been out there for a while now, but we've had a number of suspected EMC issues.  The effect of these failures is that the amplifier output freezes at a value less than 1V (Vcc=5V, Ref=1V), usually somewhere from 0.4 to 0.8V.  There are no parametric indications that the part has failed (diode measurements on all pins to all rails) when compared to a known good.

The product passes the standard panel of IEC 61000-4-* tests.  We even went back to repeat surge testing up to 6kV as our primary suspect was nearby lightning strikes.  The product will fail (when powered) with an ESD hit > 4kV.  Our feeling is that the problem is speed of the pulse more than energy.

The datasheet is very light on ESD protection.  What is the ESD spec on this part?

What would be the best method of supplemental input protection?  I currently have a 0.1uF X7R cap differentially on the inputs, the bridge impedance is about 10k/leg.  Bandwidth is not an issue for me, but simpler the better - I have very little board space available.

Any help or advice would be appreciated!