[zrato]

Seems I have found the problem thanks to jd.controlling.downloadcontroller.DownloadWatchDog.log.0

> --ID:119TS:1482976127383-29.12.16 02:48:47 - [jd.controlling.downloadcontroller.DownloadWatchDog(setFinalLinkStatus)] -> DownloadCandidate:xxx.zip@fileflyer.com|Host fileflyer.com|Account:Plugin:fileflyer.com|Version:35367|Type:NONE|Account:null|Proxy:Direkt->FILE_UNAVAILABLE

It was a download in my list that was unavailable from fileflyer.com. It was tried like every 30s. If I see it correctly, you save the download list directly into the zip, yes? Every time the download attempt started the package size/loaded MB changed, so I guess this is why an updated file was written?
Also had one similar download from sendmyway that I deleted from the list prior to deleting the fileflyer download, but that one did not change the behavior (probably because the fileflyer download was still in the list?). Now with both those downloads removed, not only did the giant copy orgies stop, the CPU usage dropped significantly and even my RAM usage dropped very significantly (2,6 GB -> 1,9 GB and still falling. EDIT: 1,7 GB now).