I have seen this behavior before, but with General BigFix actions rather than just with OSD.
When I investigated, the Operator had an incorrect number of systems reporting to them when compared to other Operators in the same Role.
We use Active Directory groups to assign Console Operators to Roles, so the fix was to remove the User from the AD group, send a blank action to all the endpoints (or just the systems manage by their Role), wait for most of the systems to report back status on the blank action, then add the user back to the group and repeat the blank action process.
Hope this helps. It happens to us about once a year or so. Seems to center around one group of Operators.