Persistent Inaccurate IP Lookup Geolocation Data for 'What is my City Name' Users: Seeking Root Cause

We're encountering a critical issue with our "What is my City Name" tool, specifically regarding the reliability of its IP lookup functionality. Despite utilizing multiple commercial geolocation APIs, a significant percentage of users report inaccurate city-level data, often placing them in a neighboring town or even a different state.

• Context: Our tool relies heavily on resolving user IP addresses to precise geographical locations.
• Observed Problem: Inconsistency in geolocation results; discrepancies between various API responses and actual user locations. We suspect issues beyond simple database staleness or VPN usage.
• Specific Technical Block: We've implemented failovers and weighted averages across MaxMind, IPinfo, and custom reverse DNS lookups, yet the core inaccuracy persists for a non-trivial user segment. We're trying to pinpoint if this is a systemic issue with how certain ISPs handle IP blocks, or if there's a more advanced technique we're missing for refining `IP lookup` data.
• Question: What advanced diagnostic methodologies or alternative data reconciliation strategies have others successfully employed to achieve sub-city level `IP lookup` accuracy, especially when commercial APIs fall short?