API Limit Reached?

I’ve been using the API to check SIC codes for our new customers. I use it sporadically but recently it only seems to complete a few requests before giving me errors. I thought it was something wrong with the code I was using but upon testing it on our own business company reg number I found it was sporadic when it would actually provide data even if I waited 5 minutes for any rate limit to reset. Have I triggered some other rate limit that requires an increase or could it be my side where the issue resides?

Rate limits are 600 requests in a 5 minute window.

If you exceed the 600 requests in a 5 minute window you will get 429.
If you go higher and exceed the AWS limit,
we ban you manually
your IP address does not match the IPs in your API restricted_ips list you will get 403.