This is likely due to using material property values near their maximum range which in turn pushes you against SDF spread limits which are determined by the Sampling Point Size to Padding Ratio.
To resolve this behavior, you can increase the sampling point size to padding ratio. where if it is currently 10%, increase it to something like 15%. This will enable you to get the same material property effective range which using values not near the maximum.
See the FAQ Question 2 and 10 in this post .