Dealing with the interior pointers bug

[TheGag96 via Digitalmars-d-learn]

I saw this Tip of the Week a while ago 
(http://arsdnet.net/this-week-in-d/2017-mar-12.html) and was kind 
of perplexed at it. It seems like a crazy potential bug... How 
exactly is the GC implemented that causes this problem to crop 
up? Does the GC just blindly scan memory until it finds pointers 
to heap memory to mark as "don't delete"? Could it ever be fixed?