Don’t you receive any error warnings when you run in the editor?
Out of bounds means that you try to access an index that is outside of array bounds, eg. there are 3 items in an array and you try to Get [3] it will be out of bounds as the length is 3 but the last index is 2 (starting with 0).
This might be no problem in editor (you should get a warning) but I imagine it might as well be fatal later on. When did this start happening? Did you work with arrays then?
EDIT: Although it seems this is happening at build time, so maybe it’s not even directly connected to your code / BP. Do you use any plugins that might cause build problems?