Spring WebFlux Reactive MongoDB - how to combine two change streams?

Question

In my app i want to combine 2 change streams to listen to changes to some filter object and to the inserts/deletes to the collection which is actually in question (to which i apply the filter residing in a different collection)

Therefore i have an approximate code like this:

public Flux<List<Object>> findAll(String userId){
        <some code here>
        return service.findByUserId(userId).
            
            < here i get initial set of data when change streams do not act >

            .concatWith(reactiveMongoTemplate
              .changeStream("Filter",options,Filter.class)

            < here i listen to changes to the filter >

            )
            .concatWith(reactiveMongoTemplate
              .changeStream("Object",options,Object.class)

            < here i listen to changes to the collection itself >

            );
    }

The problem is - second change stream is not working. This i can tell by switching them - as i switch the higher concatWith works and the one which goes below does not.

The question

Have you faced with such behavior?

What could be a better approach to do some complex listening on 2+ collections to deliver to the UI these changes?

Update

This is the whole method i have - with one changeStream working and another one not:

public Flux<List<EventDTO>> findAll(String userId){
        Aggregation fluxAggregation = changeStreamHelper.createAggregationBasedOnUserId(userId);
        ChangeStreamOptions options = changeStreamHelper.createChangeStreamOpts(fluxAggregation);
        return eventListFilterService.findEventListFilterByUserId(userId).flatMap(fltr -> Mono.just(activeEventsFilter.applyCriterion(null, fltr))
            .flatMap(criteria -> eventFilteredRepository.findEventsByCriteria(criteria)
                .flatMap(eventMapper::toDto).collectList()))
            .concatWith(reactiveMongoTemplate
                .changeStream("EventListFilter", options, EventListFilter.class).map(ChangeStreamEvent::getBody)
                .map(fltr -> activeEventsFilter.applyCriterion(null, fltr))
                .flatMap(criteria -> eventFilteredRepository.findEventsByCriteria(criteria)
                    .flatMap(eventMapper::toDto).collectList())
            )
            .concatWith(reactiveMongoTemplate
                .changeStream("Event", changeStreamHelper.createSimpleChangeStreamOpts(), Event.class).map(ChangeStreamEvent::getBody)
                .flatMap(event -> eventListFilterService.findEventListFilterByUserId(userId).flatMap(fltr -> Mono.just(activeEventsFilter.applyCriterion(null, fltr))
                    .flatMap(criteria -> eventFilteredRepository.findEventsByCriteria(criteria)
                        .flatMap(eventMapper::toDto).collectList())
            )));
    }