I suspect that your issue is related to https://issues.apache.org/jira/browse/GUACAMOLE-44
Apparently, the fix is part of the 0.9.10 release - see http://mail-archives.apache.org/mod_mbox/incubator-guacamole-dev/201608.mbox/%3CCALKeL-PDXwLGsRR5q0eSouf6jGKnfYOejZi1N0QEXBfcpZVYEA%40mail.gmail.com%3E .
Den 26. oktober 2016 klokken 08:48 skrev 吴致远 <firstname.lastname@example.org>:Hi there,
I have encountered a strange situation in RDP file transfer.
When I try to transfer a big file, say over 1 GB, it shows it is in processing but at the end, there is an pop up window saying 'An internal error has occurred within Guacamole sever...'
And then I tried again with debug on it shows guac_rdp_fs_open but never get close even the error window pop up...
And then I just try another small file 30mb, everything is fine.
Would you please look at this issue? Thank you!