The Editor will crash in PIE when an Actor calls a method in a UObject that modifies some FString members in the UObject. In the Attached project, the UObject class contains two FString members and two methods. There is also an Actor class that contains an instance of the UObject. In the Actor's constructor, the first method is called which sets the initial values for the UObject's FString members. On BeginPlay, the Actor calls the second UObject method that attempts to modify the UObject's FString members. The crash occurs when the method attempts to set a new value for one of the FStrings.
The Editor will crash when attempting to modify an FString member in a UObject.
The Editor starts PIE and the log displays some log messages from the UObject as it modifies its FString members.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-69398 in the post.