I have had this happen too. I had a fourth cousin match on ancestry that I lost yet on Gedmatch one to one comparison we are a solid match. I have another 4th cousin match on ancestry that thanks to Gedmatch I can see overlaps the match that was dropped by ancestry on the exact same spot on a chromosome. Ancestry kept one of them as a match and dropped the other one. I have a hard time seeing that case as a pile up spot since there are only 4 of us on Gedmatch who overlap on a 23 cm segment ( other cases I can see where they would be thought of as " pile ups" due to lots of matches). I am going by my one to one comparisons over on Gedmatch to tell who my matches are. I was happy to lose lots of low confidence matches with this new formula but not happy about losing ones that are show up as good matches on Gedmatch.