Blocking addresses with 0 spam attacks

Hi, I’m running a campaign and I’m seeing so many addresses blocked that have 0 IP and 0 email attacks. Or maybe 1 and 1. Why are they being blocked? I am marking them each as not spam, but it doesn’t seem to help, more people are still being blocked. People are writing to customer service stating they are being blocked as spam and want to opt-in but can’t. Those are just the very keen ones, others will just not bother altogether.

Some want to buy the product associated and can’t they are being blocked from checkout.

Is there a way to dial down the aggressiveness of blocking? Like if either IP or email is less than 5 not to block it? Or if the total is less than 10?

I have a paid subscription.