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ADG408 produces glitches on I/O pins when the select lines change

We are using a ADG408BRUZ 8:1 mux to select between 8 audio signals. When the select lines A0, A1 or A2 change, a glitch is produced within the part that propagates out of the Sx and D pins, resulting in an audible click or pop. It is clearly visible on a scope. The Sx lines are isolated from the rest of the circuit by RC lowpass filters. So we know the glitch is coming FROM the part, not TO the part. The problem goes away when the part is warmed above 25 degC, but happens whenever temp is below that. Parts exhibiting this have date codes 422. We have some other parts with date code 823 that are better, in that they must be cooled further before they exhibit this. The design will be used in outdoor environments where temp could go below 25 C. The clocks and pops are unacceptable. Any suggestions?