Hi Everybody,
shame on me… After two Days of intense searching and trying out in various ways i found out, that the Files within the Audiomontage themselves had Dropouts. How come? Before starting with the Montage, i started a Batchprocessing with Normalizing and DC-Offset Remove. I´ve done the DC-Offset remove with my UAD-Cambridge Lowcut-EQ. I guess something in that processing must have gone wrong. Unfortunaly i havent have a closer look to the Waveforms, althought i openened it in the editor… For almost 15 Years of doing Musicproductions still have to learn… 
Thank all so much who tried to help me!
elian