Everyone is bemused with the latest bug that has crept up in Mi Band 3. Incoming call notification is only showing as an icon, but not the names of caller or the number like it previously did. This is strictly a problem related to Android Pie OS. Users that are using phones running on Android Oreo doesn't have this issue. I myself faced this issue. I'm using Redmi Note 5, which runs on MIUI 10 based on Oreo, band is running smooth without the aforementioned problem. But I once installed custom ROM based on Android Pie, and immediately I faced the problem. Now I have reverted back to MIUI with Oreo, the problem is gone.
So fear not, Mi band 3 is fine. No problem in the band itself, but it lies in the compatibility of Mi fit app with Android Pie. Although, I don't know when Xiaomi is going to fix it.