When an inline function is used to execute another command, if the "Allow other commands to execute while this one is running" option is not checked in the calling command, execution will only occur once, and subsequent attempts will fail with this log entry:
"Command canceled: Another command is not allowing others to execute (canceled: command name)."
If the "Allow other commands to execute while this one is running" option is checked, the target command can be executed as expected.
If the "Allow other commands to execute while this one is running" option is not checked, but the inline function is executed synchronously(using the "Wait for the inline function to finish before continuing" option), executing another command will fail even the first time the function is used.
This is also the behavior if the "WaitForReturn" argument of the "Execute()" method is set to true.
If the inline function is run from the editor directly, the method will work regardless of command settings.
EDIT#4: Unless a command with the "Allow other commands to execute while this one is running" option unchecked is already running, as you'd expect.
EDIT: Also applies up to v1.7.5.4
EDIT#2: Also applies to v1.7.5.8
EDIT#3: Also applies to v1.8.3.21