This was experienced in UE 5.01 - custom installed engine (No changes to UE code, simply added the Debug build configuration, see the following command):
-target="Make Installed Build Win64" ^
I first noticed this in my own project when building in Debug mode - it persisted even after I removed all user-defined content from the world outliner and disabled all user code which touch FVectors. So I tried to repeat the process on a new empty project and discovered that it is reproducible in that context, too.
This error is not debugable since, either due to FORCEINLINE or ENABLE_NAN_DIAGNOSTIC, a breakpoint either can't be set on it (VS) or is not honored during debug runs (Rider). I spent a great deal of time trying to find the cause of this issue because I wanted to resolve it to ensure that it was not contributing to another problem I'm facing in my project - it has taken a long time to narrow down the conditions under which it emits.
The error appears to emit for all packaged Debug builds - this should be fixed.
Also, the error should be attributable to specific engine or user code. Currently, there is no way to discover where it comes from. I spent too long tracking this down, initially thinking it was related to some other problem I am facing in my project.