my public IP address acting weird?

hey folks, so our little 'what is my IP address' tool, which is supposed to be a simple IP lookup, is acting a bit... moody. sometimes it's spot on, but other times it's giving us some really inconsistent results, or even showing a proxy IP when we know we're direct. it's kinda messing with our user experience.

// example output
Actual IP: 192.0.2.1
Tool Reported: 10.0.0.5 (private range?!)
// another case
Actual IP: 203.0.113.10
Tool Reported: 198.51.100.25 (some random proxy?)

any ideas what might be causing this weird public IP behavior?