My inspection of the UE 5.1 source code (this was 5.1.0, not 5.1.1, but I doubt this section changed much) and the log messages suggested to me that the error happens when UE calculates a finite overall landscape size but a cell size of zero (or something that rounds to zero with floating point precision limits). The code determines the number of cells by dividing the overall dimension by the cell size, so the number of cells is incorrectly determined to be infinity, or an extremely large number.
I still haven’t quite deciphered where or how the cell size is determined. I’m experienced in programming C#, Java, and C but am just learning C++, and the UE engine source is an unfamiliar and complex code base without a lot of embedded comments. The upshot is that I understand the local logic and what it’s doing with the data, but I’m not certain where the data originates that it is receiving. (I should also mention that I’m a Linux guy normally, and Visual Studio is a brand-new IDE for me and not what I normally use, so I haven’t learned the VS debugger yet.)
I’m sorry not to be more helpful on this issue. I have to balance working this problem against my company’s project deliverables that don’t depend on this specific task. I haven’t given up on solving this and contributing a solution, but it may not be as soon as I would prefer, and I’d welcome any input from experienced C++ coders.