Missing events even with flush

I am sending 13 events with logEvent at about the same time. I am not awaiting for the promise to resolve.
Later on, before I terminate, I am calling flush to make sure all events will be sent.
Flush responds with status: skipped

## Expected Behavior

All events to be logged

## Current Behavior

Some events are missing, sometimes 1, sometimes more

## Possible Solution

I guess the request is still ongoing for some events?
But flush doesn't know about it?

## Steps to Reproduce

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## Environment
- SDK Version: 1.6.1
- Node version: 12.x