ISSUSE occurs when using BTGuard Node!

[lcfzblcfzb]

I am new to the behavior tree,still learning .
today I create a test project and try build one simple behavior tree. looks like thi

s:
I use a parallel node as root, and first child of root is response to scan the target, measure the distance between. and CheckFound is also the lock and unlock object of BTGuard node (true->unlock,false->lock)
second child of root is the BTGuard node,which I want to be unlock when target is found.

when I run the test ,this error appears:
"Invalid BTNodeState assignment. Can only set to success or failure."

the debug result shows that when executing the tick() method of the Selector Node, its already running, so in the _tick() method of
BTGuard ,it get a result of false ,and child state is still running.

maybe I've misuse the BTGuard node because Im new to behavior tree ,but still want to know when and how to properly use BTGuard and do not run into problems!