You shouldn’t need to keep creating account registrations - 1 is almost always enough. I’m not familiar with le64, but you should look into their documentation and see if there’s a way to specify an account key or something so that it doesn’t keep attempting to create accounts.
You can create a maximum of 10 Accounts per IP Address per 3 hours. You can create a maximum of 500 Accounts per IP Range within an IPv6 /48 per 3 hours. Hitting either account rate limit is very rare, and we recommend that large integrators prefer a design using one account for many customers.
Edit: The ACME protocol, and Let's Encrypt, are kind of in the middle of replacing the term "registration" with "account". But they're equivalent.
It would still be helpful to figure out why it is creating a new account every time, because it’s not necessary to do so in order to get a new certificate.