I'm a beginner to bioinformatics so hopefully someone can help with my question! I am trying to go from GRCh37 to GRCh38 for a large number of SNPs. I have an input bed file of around 700,000 SNPs that I have used for NCBI remap, ENSEMBL Assembly Converter, and Liftover (UCSC). These websites all give different numbers of SNPs that are not in the new build with little overlap of SNPs between websites. I am doing an assembly conversion because I want to have the new physical positions for the SNPs. I know that rsID's can change between assemblies and am wondering if these websites would work best for that? Would the best way be to combine all the SNPs that do not match to the new build (from all three websites) and get rid of those or is there another way to do this? Thank you very much.