All right - so ...
- Here's a good article on troubleshooting agent discovery (also - take note of my comments @ the bottom) - How to troubleshoot Agent Discovery - that should help along a little bit.
- While you & your colleague are using the same Core, are you using it both via RDP (i.e. - you RDP to the Core & open up the console once there), or do you have your own remote consoles installed?
- I'm guessing your colleague is "local admin" of the device / console he's working on. Are you sure you are? Reason I ask is that Microsoft networking behaves differently when you're a local admin versus not (usually something that trips people over when running UDD scans). It's one of those things that doesn't make a lot of sense but "it's a thing".
Agent discovery works on the relevant Console (be it on the Core or a remote one) trying to do a background discovery (essentially "a ping" on port 9595) to the relevant device. There's a bunch of ways that this can usually go wrong:
- DNS is not correct / leads to incorrect device. DNS can have different results for different users, which could cause what you're seeing.
- The article I linked includes the use of the "Diagnostics" & real-time discovery (https://community.landesk.com/docs/DOC-35474#jive_content_id_Check_Client_with_Realtime_Discovery) - that provides a lot of useful information in one go & usually helps explain what's going on (especially whether the right device is responding back).
... that should be enough to get you started.
I figure / suspect that each set of results is "correct" from its own vantage point - it's just that you've got some networking shenanigans going on (for whatever reason) - but armed with the article, you will have plenty of information in how to track it (Wireshark is awesomely helpful) and what you need to do .
Hope that helps.