Issue with AWS - "Concurrent Mutation Limit Exceeded"

I’m running into this issue when trying to creat a client VPN endpoint on AWS using Terraform. The VPN uses several split-tunnel routes which I’m injecting using count in the resource. The problem is that once terraform apply is executed, at some point the AWs API returns the following errors:

16:02:40 Error: error creating client VPN route “cvpn-endpoint-07893519893e88e5a,subnet-0dbfb0b3cfbf76622,”: ConcurrentMutationLimitExceeded: Cannot initiate another change for this endpoint at this time. Please try again later. 16:02:40 status code: 400, request id: 8516529b-4418-4e6a-a907-44d25a7c78c7

I opened a case with AWS and they responded to me saying: "Secondly, the error is regarding limit on number of concurrent mutating actions allowed on a Client VPN endpoint [1]. We cannot have more than 10 endpoints resource (association, routes, rules or SGs) in “pending” or “creating” state. We will have to wait for the pending actions to be completed before we can issue more mutating API calls.

Finally, I would suggest to build your code logic to wait between API calls mutating the Client VPN endpoint to avoid this error in future."

I’ve tried execution with ‘-parallelism=1’ but this hasn’t helped.

Would you know what else I can try?