Hi developer, I found that every command executed returns with "Total output of XX bytes was truncated at 0 bytes." message. I Googled and found https://sourceforge.net/p/webadmin/mailman/webadmin-list/thread/0ABC8F4068A6204785BA927C8661371513A038%40ex04.f5host.local/#msg32866715 but my /etc/usermin/shell/config file is blank.
This is a bug in Usermin - the work-around is to create the file /etc/usermin/shell/config containing :
max_output=100000
max_runtime=86400
The next release will fix it properly.