Zendesk requests endpoint rate limit

Howdy we are using the api 

api/v2/requests

to create tickets in our backend in zendesk. The volume is generally pretty low that we are sending to this endpoint as far as we can see on our end. But we are still seeing cases during certain parts of the day where we get a spike of failed requests due to a 429 status code . I have been reading through the documentation but couldn't find any specific rate limits mentioned being applied to this endpoint specifically. Is there any.

I have attached a screenshot of our api activity graph and we are no where close to our requests per minute. So surprised we are getting rate limited.