Question Duplicate shader works, original does not

I stripped my shader down to figure out why the vertex colors weren't working. No change I make seems to get it to correctly display vertex colors, except making a duplicate shader. The problem is on Android, Unity 2019.4.16f1. URP 7.5.3. It is a fragment shader. In the non working state, the fragment shader just returns white. What could cause an identical copy (except for the name) of a shader to work, but not the original, referenced from the same material?