Heartbeat issue?

Hi! I have a Spring Boot 2.x Vaadin version 14.2.1 app, running in v.13 compatibility mode. I debugging strange behaviour of abnormal app reloading, and experimenting with different options. I noticed when vaadin.productionMode=true I do not see heartbeat messages in browser’s console. Is it expected behaviour (maybe these messages hidden?)? If not, then why there are no heartbeat messages, any ideas?