If you’re seeing warnings about replaced parts, check Settings > General > About > Parts and Service History.
That will show which part is involved and whether iPhone identifies it as Genuine, Used, Unknown, or says Finish Repair. An “Unknown” message can mean the part isn’t genuine, isn’t working as expected, or wasn’t properly verified after the repair.
If you can post the exact three warnings you’re seeing, that would help narrow down which part needs attention.
iPhone Parts and Service History - Apple Support