You have Box Securlet enabled and you notice the Box Securlet API calls are getting 429 errors because the number of calls have exceeded the Box API quota. This is causing delays in content inspection and other performance issues.
Or you may already have two additional Box Securlet Co-Admin accounts created to split up the Box Securlet API load, but you are still getting 429 errors.
There are other application or applications that are sharing the same Box Admin Account with the Box Securlet and sending API calls.
Create a new Co-Admin Account for the additional application to avoid sharing the API quota with the BOX Securlet.