PolicyNotFoundException thrown intermittently despite previous requests being successful

We've been having a weird issue for a while, where an API endpoint that is working, suddenly starts failing with the following error:

{
"responseCode": 500,
"message": "Policy not found: plugin:io.apiman.plugins:apiman-plugins-cors-policy:1.4.3.Final:war/io.apiman.plugins.cors_policy.CorsPolicy",
"trace": "io.apiman.gateway.engine.beans.exceptions.PolicyNotFoundException: Policy not found: plugin:io.apiman.plugins:apiman-plugins-cors-policy:1.4.3.Final:war/io.apiman.plugins.cors_policy.CorsPolicy
}

The exception doesn't make sense since the endpoint was working and the plugin obviously exists.
Assuming this exception is a red herring and something else is actually blowing up. It's also not related directly to the actual plugin because we've seen various plugins referenced in the exception. I.e. It's not specifically with the CorsPolicy plugin, this just happens to be the plugin for this endpoint.

The only solution once this starts happening is to restart, where the call once again starts working again.