Hey @cdav,
I referenced this issue on this thread recently. It's operating as designed - if you were targeting a JSON file hosted on an external GitHub repo for your IP feed, if the certificate changes, you'd want to update the certificate to avoid any secuirty issues. As a result, the gateway will clear the object cache until you accept the new certificate, impacting traffic in the process.
This is a current concern of ours. We're starting to use more of these objects in our production firewall policies to enable application owners to automate traffic flows specific to their application. It's become crucial we track certificate expiry dates to avoid impact in production. I've got an open SR with our Diamond Engineer to investigate possible workarounds to this issue. I'll update this thread if I get anywhere with it!