N/S/R/ Door jammed shut
 

My brother has a minted 1994 S class 420 and no computer/internet so asked me to help. His problem relates to his N/S/R door being jammed shut the "feel" of both inside and outside handles is normal, central locking working OK. managed to get door panel off and saturated the complicated mechanism in oil and the right components all seem to be moving fully ( have taken off O/S/R/ door panel for comparisons) I thought the Jag door mechanism was over engineered but this beats it hands down. We are both reasonable mechanics but are totally stumped. Any help would be much apprieciated.