Hello, I have an SNP dataset of 717014 SNPs and a very small sample size (145). I have 50 traits that are quantitative. I have estimated the SNP-based heritability using the GCTA tool. And for most of the traits, I have got pretty good estimates with SE (0.1 to 0.2). But with the same sample size, I have got heritability estimates of "0" and 0.99999. Can you please explain why has that happened or how can I interpret it?

Thanks. Anik