High CPU utilization by the RAD daemon may just be the symptom, not the cause.
Are you sure that any routers/switches your organization manages upstream of the firewall have not been replaced? Upgraded? Any new DoS defenses or web content caching? Mirror and decrypt to store HTTPS traffic for compliance/regulatory purposes?
Next step is to have a frank discussion with your ISP, and I don't mean with their sales guy. Have they recently introduced some kind of "helpful" DoS protections or Intrusion Detection/Prevention? Started shaping/limiting traffic due to their network being oversubscribed? (doubt they'll admit to this without some harsh conversations) Changed or reduced their peering with the rest of the Internet? Are you located in a country that might be interfering with Internet traffic in any way due to geopolitical concerns or having their enemies doing the same? I had a student attending a class from Russia last month and they kept getting disconnected, and had to keep routing through different VPNs to be able to continue attending my class hosted from the USA.
If you have any historical metrics you can use to assess your Internet bandwidth I'd strongly recommend taking a good long look at them; my guess is you will find something has changed upstream.
Edit: See this response: https://community.checkpoint.com/t5/General-Topics/RAD-issues-Timeout-and-quot-RAD-request-exceeded-...
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