Wrong Time Zone Autonomically changes

I have a user whose time zone keeps reverting to CST even though he's physically in EST. He travels for work and was recently in Mexico, returning this week — the issue started shortly after he got back.

I've already confirmed:

• Time zone is set to update automatically (On)
• Location services are enabled (On)
• He is not connected to VPN

After a recent Windows Update and restart, the time zone corrected itself to EST and held for the rest of the day, but then reverted back to CST on its own.

Is there anything else I can troubleshoot on my end to resolve this? Ideally I'm looking for a fix that addresses the root cause rather than disabling automatic time zone detection — since he travels internationally for work, I'd like the auto-detection to keep working correctly rather than have him manually switch the time zone every time he changes locations.

Thanks for the help.