Notification error? Related to overlay

[Tomoko]

I lost a group without being told, so I thought one that I was in had just been deleted, fair enough. I had 0 notifications but HADN'T checked my invite second.

I get in game and open up my overlay and it turns out I had "1 new invite", which was me being dropped from a group, 3 hours earlier.

This notification was not sent on the steam client upon logging in, but it was sent on the overlay version (Specifically in CS:GO).

Is this a known issue, or am I having a very specific glitch with my pc?