we found that you have to disable the ClientUI. You can’t use the existing fixlet “BES Client Setting: Client UI Enable/Disable Main Dialog” because it is only relevant on systems with Internet Explorer, which Core edition does not have.
I made a copy of the fixlet that worked and allowed the reboot to succeed:
Relevance:
if (version of operating system >= "6.2") then (((exists value "ServerCore" whose (it as string = "1")of it AND not exists value "Server-Gui-Mgmt" of it AND not exists value "Server-Gui-Shell" of it) OR (exists value "ServerCore" whose (it as string = "1")of it AND exists value "Server-Gui-Mgmt" whose (it as string = "1")of it AND not exists value "Server-Gui-Shell" of it)) of (key "HKLM\Software\Microsoft\Windows NT\CurrentVersion\Server\ServerLevels" of native registry)) else false
not exists setting "_BESClient_ActionManager_UIEnableMode" whose (value of it = "none") of client
ActionScript:
setting "_BESClient_ActionManager_UIEnableMode"="none" on "{parameter "action issue date" of action}" for client runhidden cmd /C net stop besclient && net start besclient > NUL 2> NUL