Urs, after updating FSAerodata with AIRAC 1808 and disabling and enabling it again, I got a clean DB build. The double entries of DME's in Rhodes and Dalaman have also gone. But...I noticed some other DME's with double entries as Basel BLM 117.45 and Saronno SRN 113.7. Maybe there are a few more around the globe but as EFB is running without problems, I think we can leave it as it is. Thank you and all others for your help.
Rgds Roland