Springboot WebFlux tests failing after upgrade to spring boot 2.2

I have some Springboot integration tests which worked fine in Springboot 2.1 but now that I have upgraded to Springboot 2.2 they're failing. Using default spring-boot parent dependency management. Some failing tests which used to work are as simple as this example:

...
@RunWith(SpringRunner.class)
@SpringBootTest(
 webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT,
 properties = {"spring.sleuth.enabled=false"})
@Import({AccountApiClient.class,...})
@DirtiesContext
@AutoConfigureStubRunner(stubsMode = StubRunnerProperties.StubsMode.CLASSPATH,
 ids = {"my.org.com:account-service:+:stubs:9021"},
 consumerName = "AccountServiceV2",
 stubsPerConsumer = true)
public class AccountsClientTest {

@Autowired
AccountService accountService;

@Test
public void verifyAccountsShouldReturnEmpty() {
    Mono<List<Accounts>> acc = accountService.getAccounts(new AccountId(ACC_ID));
    assertThat(acc.block(), hasSize(0));
 }
 ...

Before the upgrade, this test passes as expected but after the upgrade, it fails with the following error:

[ERROR] verifyAccountsShouldReturnEmpty  Time elapsed: 0.004 s  <<< ERROR!
reactor.core.Exceptions$ReactiveException: java.lang.AssertionError: Spring Context [org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@7d605944, started on Tue Aug 18 10:00:09 CEST 2020, parent: org.springframework.context.annotation.AnnotationConfigApplicationContext@a035db9] is not yet refreshed. This is unexpected. Reactor Context is [Context0{}] and name is [blocking]

I have many tests with similar behaviour after upgrading and have been stuck with this issue for a few hours already. It fails on line assertThat(acc.block(), hasSize(0));

Any ideas on what's causing it and how to fix would be greatly appreciated.

Thanks.