Strange Input Current in ADA4084-1


I am using the ADA4084-1 in a non-inverting, follower configuration in a data acquisition application.  The input is AC coupled.  At high input power levels, the input suddenly latches to a high value, and will stay there until the input RMS voltage is brought down.

Here is the circuit.Schematic

Here is the (yellow) input at R26, for a small RMS input voltage (purple).

Good follower

When a larger input voltage is selected, there is suddenly a large offset in the input voltage.  Why?

Naughty follower

Thanks for your attention.