Well…now it’s just being mean. 
The only thing I can think of to do would be to keep unhooking nodes a few at a time and keep closing/opening the project to see if the error is there. If it is always going to show green arrow regardless, you would have to actually play through each time to the part that it bugs as well. Eventually, you could at least find out which part of the code is causing the trouble.
I realize if we are talking about an absolutely huge blueprint, this might not be a viable option. I’m stumped on what else to do though. The code in your screenshot doesn’t seem problematic. It is just subtracting one vector from another and plugging it into the new location. The only node that might be of issue is the get attach parent actor, but I’m assuming you would have already checked a long time ago if there wasn’t parent attach in world outliner (what I believe that node is used for? But, I don’t use it that often).