When a long running query is executed MongoDB tries to acquire storage statistics. If the lock request for that operation times out, it fails with the following message:

[conn4650] Timed out obtaining lock while trying to gather storage statistics for a slow operation

Then, we can see that the cursor is killed:

Error in $cursor stage :: caused by :: operation was interrupted" errName:CursorKilled errCode:237 reslen:292

That query needed 257292ms to execute, to then get killed because it couldn't acquire a global lock to gather statistics (500ms timeout).

I think that in the cases where the lock request timeouts MongoDB should skip the gathering instead of killing the cursor.

Edit:
We already skip storage statistics collection in case of a failure to obtain MODE_IS global lock. In such a case an error is reported but the query proceeds as normal.
This ticket should root cause the reason why the query failed with CursorKilled. A failure to obtain MODE_IS global lock might be hinting towards the state of the system.