C# Linq Query Bad Translates to the RQL in RavanDB

I have an old project that was developed by the .Net framework and RavenDB 3 ... I'm trying to migrate the RavenDB to the 5.* version there is weird behavior in translate a Linq query to the RQL query

The below codes in c#

var query = documentSession
    .Query<Documents_ByOrgan.Result, Documents_ByOrgan>()
    .Where(x => x.OrganisationId == request.OrganisationId);

query = (from result in query

        let onboarding = RavenQuery.Load<IOnboarding>(result.OnboardingDocumentId)
        let onboradGroup = RavenQuery.Load<IGroup>(onboarding.Group.DocumentId)
        let invitedBy = RavenQuery.Load<User>(onboarding.InvitedByUser.DocumentId)                    
        let siteDoc = RavenQuery.Load<Site>(((Team)onboradGroup).Site.DocumentId)
        
        select new
        {
            OnboardingId = onboarding.Id,
            ...
        }).ProjectInto<T>();

Translates to the RQL in this way :

declare function output(result, onboarding) {
    var onboradGroup = load(id(onboarding.Group));
    var invitedBy = load(id(onboarding.InvitedByUser));
    var siteDoc = load(onboradGroup.Site.DocumentId);
    return { ... };
}
from index 'Onboardings/All' as result 
result.OnboardingDocumentId as onboarding 
select output(result, onboarding) 

Why

let siteDoc = RavenQuery.Load<Site>(onboradGroup.Site.DocumentId)

translates to :

var siteDoc = load ( onboradGroup.Site.DocumentId );

BUT

RavenQuery.Load<IGroup>(onboarding.Group.DocumentId)

translates to the:

var onboradGroup = load ( id ( onboarding.Group ) );

how can I prevent from generating id(..) in RQL?

id(..) doesn't load any document

there is a lot of these queries in my project and all of them works fine with the 3.x version

In addition, I have the below config :

documentStore.Conventions.FindIdentityProperty = memberInfo => memberInfo.Name == "DocumentId";

there is a discussion here that helps me to find the problem