Thanks for posting your question on the forum!
I'm not aware of any issues as that. The first thing I would recommend doing is turning on "debug cry ike" and log the output as a file transfer is taking place. Also, take a look at the Shrew log and see what it is seeing.
Is it happening with all the file transfers or just a certain file? Is it happening with a file transfer in one direction or in both directions?
Please do not hesitate to let us know if you have any questions.
If this is only happening with large files, but small files download successfully, it could be a packet fragmentation problem. In this case packet capture with wireshark/tcpdump would show 'segment lost' errors. You can try setting the MTU of the NIC at a smaller size on the client machine, e.g. 1400, 1380, 1340, etc. to see if at some point the download succeeds.