解决方案是捕获刷新令牌时导致的500，然后使用下面的类启动新的授权流：

import org.springframework.security.oauth2.client.*;
import org.springframework.security.oauth2.client.registration.ReactiveClientRegistrationRepository;
import org.springframework.security.oauth2.client.web.DefaultReactiveOAuth2AuthorizedClientManager;
import org.springframework.security.oauth2.client.web.server.ServerOAuth2AuthorizedClientRepository;
import org.springframework.util.Assert;
import reactor.core.publisher.Mono;

/**
 * A delegating implementation of ReactiveOAuth2AuthorizedClientManager to help deal with a 500 Internal Server Error
 * that is a result of an expired access token. With ReactiveOAuth2AuthorizedClientManagerCustom, we manage to redirect
 * to the login page instead of returning a 500 Internal Server Error to the user/client.
 */
public class ReactiveOAuth2AuthorizedClientManagerCustom implements ReactiveOAuth2AuthorizedClientManager {

    private final ReactiveClientRegistrationRepository clientRegistrationRepository;
    private final ServerOAuth2AuthorizedClientRepository authorizedClientRepository;
    private final ReactiveOAuth2AuthorizedClientManager authorizedClientManager;

    public ReactiveOAuth2AuthorizedClientManagerCustom(ReactiveClientRegistrationRepository clientRegistrationRepository,
                                                       ServerOAuth2AuthorizedClientRepository authorizedClientRepository) {
        this.clientRegistrationRepository = clientRegistrationRepository;
        this.authorizedClientRepository = authorizedClientRepository;
        this.authorizedClientManager = new DefaultReactiveOAuth2AuthorizedClientManager(
                this.clientRegistrationRepository, this.authorizedClientRepository
        );
    }

    public Mono<OAuth2AuthorizedClient> authorize(OAuth2AuthorizeRequest authorizeRequest) {
        Assert.notNull(authorizeRequest.getClientRegistrationId(), "Client registration id cannot be null");

        return this.authorizedClientManager.authorize(authorizeRequest)
                // The token has expired, therefore we initiate a new grant flow
                .onErrorMap(
                        ClientAuthorizationException.class,
                        error -> new ClientAuthorizationRequiredException(authorizeRequest.getClientRegistrationId())
                );
    }
}

然后添加下一个@Bean

public ReactiveOAuth2AuthorizedClientManagerCustomConfig(ReactiveClientRegistrationRepository clientRegistrationRepository,
                                                             ServerOAuth2AuthorizedClientRepository authorizedClientRepository) {
        this.clientRegistrationRepository = clientRegistrationRepository;
        this.authorizedClientRepository = authorizedClientRepository;
    }

    @Bean
    @Primary
    ReactiveOAuth2AuthorizedClientManager authorizedClientManager() {
        return new ReactiveOAuth2AuthorizedClientManagerCustom(
                this.clientRegistrationRepository, this.authorizedClientRepository
        );
    }