_deleted incorrect statement_

Well, that's certainly not the case. Each satellite transmits a low-precision almanac to the receiver that helps it lock onto the others, as well as a higher-resolution ephemeris that provides the necessary pseudorange accuracy for that particular SV.

But it's true that neither of those factors accounts for miles of error. That has to come down to either poor sky coverage/signal strength, poor software, or (more likely) both.