I have the same issue, starting after upgrading a project from 5.0 over 5.1 to 5.2.
Logically, the project is working fine, but as soon as I start visually debugging a character reference in a Blueprint Editor and hovering over the node that this reference is returned from, the engine freezes endlessly, until I close it from the Windows Task Manager.
During the freeze the engine uses 1-3% CPU and ~16 GB memory, but my system is never going above ~32 / 96 GB total memory.