It is possible to create spline logic that will not be detected by infinite loop detection.
Also hangs if executed in Event Graph on Begin Play.
If saved but not compiled and placed in Editor Startup Map, Editor will hang on startup.
Confirmed in MAIN 4.23 @ CL 5422545
Result: Editor hangs indefinitely
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-71676 in the post.