Multicast works, but gets stuck before finishing

[Krautkopf]

Hi,
All switches are configured to support multicast and the clients also join effectivly the multicast session and start to clone the partition. During the partclone process they get stuck before finishing (depending on the image at 53%, 83%…). I tried different images, hosts etc without success.
Unicast sessions work without any problems.

Any ideas?
Best regards