How to find FIS GEOMETRY boundary between value and NaN

While getting smaller the geometry polygon is, the returned value turns to NaN. How can I find this boundary value? I need to list test items very soon.

Value returned. 70.000000000,25.000000000 70.000000001,25.000000001 70.000000001,25.000000001 70.000000000,25.000000000 70.000000000))

NaN returned. 70.0000000000,25.0000000000 70.0000000001,25.0000000001 70.0000000001,25.0000000001 70.0000000000,25.0000000000 70.0000000000))

I do not know the answer to your question, as I believe it is somehow related to calculation rounding, and it depends on the CRSe, etc.
Can you explain, what you would like to do? The first polygon, the one that is working, is already so small, that it will be a “point” for just about any satellite mission. If I am not mistaken, this is less than 1cm2. Comparing this to 10x10m Sentinel-2 pixel or 160x160m CLOUDLESS pixel, it does not really make any difference if you go to even smaller.