My experience has been cyclical, as long as you stick to IPv4 with good SPF and your reverse DNS works it will work 95% of the time. The remaining 5% appears to be completely random however.

It’s possible that my issue was too low a traffic to ‘hold onto’ my score with Gmail, since it was one domain and one email address. With some luck you should be able to have enough traffic to avoid that. Best of luck.