Spawning error killing fps, actor isn't valid?

Hi, Ive set up a system for spawning enemies on top of a train in a way so they don’t overlap, but the problem is after i kill a certain amount it starts to drop alot of frames and then i get a ton of PIE errors, saying that theres a problem with my branch which set the “death” to spawn another enemy in its place, i did some research and found out that its got something to do with my actor not being valid, but i have no idea why it wouldnt be and what i can do to make it valid and stop killing my frames.
thanks in advance!!

https://gyazo.com/7368efbf3c22b9c7c316449d1ac52b2

Pictures i meant to send^^

fixed it:P