In this Letter, we report on the short and long term dynamical behavior of water vapor sorption-desorption cycling on catalytic active nanoclustered Pd:Ag particles packed into compressed thin wafers. The water vapor desorption kinetics, following a hydration session, was monitored using conventional photoacoustic (PA) detection and relative humidity monitoring. It was found that the dehydration process was always accompanied by oscillations, with a period of the order of minutes. These observations are tentatively explained in terms of a PA model appropriate for damp porous materials in which we incorporated a term to describe these oscillations as arising from a competition between reactive sorption processes on the Pd:Ag surface.