Thanks for the quick response! I apologize for the gray-on-white text, probably due to a browser extension I had a similar thought in mind, so I went ahead and set the "Server keepalive interval" to 10, in the "Session/Environment" configuration section. After about 10 minutes of idling I still experienced the same issue: all SFTP actions failed with errors such as: "Unable to read file", "Unable to open file" and "Unable to write to file" in guacd logs. In addition, I tried setting "ClientAliveInterval" to 10 on the SSH server's /etc/ssh/sshd_config file, still no luck. I took a quick look at the code in guacd doing the "keep-alive"-ing, and could not find anything off about it.
The thing I find most weird about this, is as I mentioned, the SSH session remains fully functional after the idle duration (running shell commands, reading/writing files). It seems to be a problem with SFTP in particular
