We recommend exploring the hg38 and hg19 GRC Incident tracks, which highlights areas where assembly issues have been identified or resolved by the Genome Reference Consortium (GRC). It is important to note that mappings between genome assemblies are not always symmetrical, so you may encounter differences when lifting between assemblies (e.g., from hg19 to hg38). These discrepancies are expected, as regions in new assemblies may shift, and corrections for previous assembly errors (such as bad data) are made, which is reflected in the GRC Incident track. We also recommend reviewing the liftOver tracks on hg38 and -hg19 +hg19 to visualize the liftOver alignment and identify which parts of the input region overlap or don't overlap. Both hg38 and -hg19 +hg19 include Diff tracks that show exactly what regions are included, excluded, or differ between the assemblies, as well as any changes in the contigs used to assemble specific regions.