Probably fiddle with mask-textures compression settings and/or mip generation method. Try setting a sharper mip generation, it might solve it from close-up.
This might also be an issue with your image itself, where the values don’t actually meet properly in the middle and there is a gap between the squares. This could also be some texture filtering, so mess with bi-linear filtering/point sample filtering.
Hope one of these solutions works for you!