Some suggestions for developers:
- Add a safe mode to start JDownloader with safe settings with full error log.
- In the future, it will be nice if there could be added some protection mechanism to check for corrupted data before the whole file has been downloaded. A safe mode could download a file with half of the speed, but checking the data two or more times with a lot of small concurrent downloads. This feature probably will be only possible for premium users and only in hosts which support concurrent chunck downloads.
- Dont know if this is already coded in JDownloader, but there are some secure network algorithms to prevent corrupt downloads and redownload only the bad parts. I know basic protection checksum is already implemented in TCP protocol, but it will be wonderfull to add an internal more secure algorithm to prevent bad downloads and download only the bad corrupted parts. (Having to redownload a corrupted 2GB file is a pain).

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Just to add that JDownloader nowadays is a lot better and much more stable. There are less CRC errors and I have seen improvements in connections to servers and download managing. The tips above wont be probably needed but its always a good resource to check for common solutions.