After upgrading to 26.7.3_8 the WAN interface was up but there was no route to the internet, and the radix issues were back in the log. In System -> Gateways -> Group there is a WAN Backup with only a Tier 1 gateway defined. As a test, I added the same gateway as Tier 2 and connectivity to the internet was restored. I've used a backup WAN long ago when switching providers, and removed the interface after migration, but it seems I didn't clean up the gateway group at the time. No radix issues in the log anymore. I will remove the group since I'm not using it anymore.
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