Came across this node:
Documentation says “Takes an array of strings and removes any zero length entries.”
How is this supposed to work if the input is a single string and not an array?
That function seems to be badly exposed to BPs.
FString::CullArray is a static function, but the BP version is still taking a string instance to operate on (which it won’t mutate as the function is static), and takes the array as an in/out argument (which doesn’t really work with BPs).
The BP exposed function should probably be changed to take an array, internally make a copy, call FString::CullArray on the copy, and then return the result. I’ve raised UE-45185 to fix this 
still an issue in UE5 