Upgrade Flightstones/Crests - issue

when I try to use the function in question it gives me many false upgrades. For example it gives me the “Globe of Jagged Ice” trinket at 437 with an improvement of 2.80%, but if I use the “Mythic+” function the same trinket (always 437) gives me -0.28.
Who should I believe???

If you post a snapshot ID we can take a closer look at your case and see what is going on. Instructions on how to do that here:

This snapshot ID for the Flightstone/Crest 3c3a3df4a3a346dfaa26bf13443d3776 when the “Globe of Jagged Ice” trinket at 437 with an improvement of 2.80%.
This snapshot ID for the Mythic+ 80b921fa18ae472eae1020880c13567e when the “Globe of Jagged Ice” trinket at 437 with an improvement of -0,28