Another instance with the key value '' is already being tracked in 1:n relationship

I'm trying to update an entity Tender, this entity has a List of TenderOffer and this TenderOffer has a Company entity. When I try to update the Tender I'm getting the following error

Message=The instance of entity type 'Company' cannot be tracked because another instance with the key value '{ID: 4}' is already being tracked. When attaching existing entities, ensure that only one entity instance with a given key value is attached.

Source=Microsoft.EntityFrameworkCore  StackTrace: 
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.IdentityMap`1.ThrowIdentityConflict(InternalEntityEntryentry) 
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.IdentityMap`1.Add(TKeykey, InternalEntityEntry entry, Boolean updateDuplicate) 
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.IdentityMap`1.Add(TKeykey, InternalEntityEntry entry) 
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.IdentityMap`1.Add(InternalEntityEntryentry) 
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.StartTracking(InternalEntityEntryentry) 
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.SetEntityState(EntityStateoldState, EntityState newState, Boolean acceptChanges, BooleanmodifyProperties) 
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.SetEntityState(EntityStateentityState, Boolean acceptChanges, Boolean modifyProperties,Nullable`1 forceStateWhenUnknownKey) 
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.EntityGraphAttacher.PaintAction(EntityEntryGraphNode`1node) 
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.EntityEntryGraphIterator.TraverseGraph[TState](EntityEntryGraphNode`1node, Func`2 handleNode) 
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.EntityEntryGraphIterator.TraverseGraph[TState](EntityEntryGraphNode`1node, Func`2 handleNode) 
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.EntityEntryGraphIterator.TraverseGraph[TState](EntityEntryGraphNode`1node, Func`2 handleNode) 
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.EntityEntryGraphIterator.TraverseGraph[TState](EntityEntryGraphNode`1node, Func`2 handleNode) 
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.EntityGraphAttacher.AttachGraph(InternalEntityEntryrootEntry, EntityState targetState, EntityStatestoreGeneratedWithKeySetTargetState, Boolean forceStateWhenUnknownKey)
   at Microsoft.EntityFrameworkCore.Internal.InternalDbSet`1.SetEntityState(InternalEntityEntryentry, EntityState entityState) 
   at Microsoft.EntityFrameworkCore.Internal.InternalDbSet`1.Update(TEntity entity) 
   at DAL.Repositories.TendersRepository.<UpdateTender>d__10.MoveNext() in C:\Progetti\DAL\Repositories\TendersRepository.cs:line 613 
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() 
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) 
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) 
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult() 
   at UI.Controllers.TenderController.<SelectTenderWinner>d__13.MoveNext() in C:\Progetti\UI\Controllers\TenderController.cs:line 808
            
This exception was originally thrown at this call stack:
                [External Code] DAL.Repositories.TendersRepository.UpdateTender(ML.Models.Tender) in TendersRepository.cs
                [External Code]
                UI.Controllers.TenderController.SelectTenderWinner(int,int, bool) in TenderController.cs

I don't understand why I'm getting this tracking error. I have disabled all tracking behavior of the constructor of the DBContext

base.ChangeTracker.AutoDetectChangesEnabled = false;
base.ChangeTracker.LazyLoadingEnabled = false;
base.ChangeTracker.QueryTrackingBehavior = QueryTrackingBehavior.NoTracking; 

I'm also using AsNoTracking() in all my queries. I can't figure out why EF core is tracking anyway.

The entity_one is "Tender", the entity_two is "TenderOffer"

This is the code in the controller:

try
{
    //id and winnerOfferID are parameters of the request

    Tender tender = await this._tenderRepository.GetTender(id, false, this.CurrentCompanyID);
    TenderOffer offer = tender.TenderOffers.FirstOrDefault(o => o.ID == winnerOfferID)
    tender.IsClosed = true;
    tender.ClosureDate = DateTime.UtcNow;
    tender.ShowWinner = showWinner;
    tender.WinnerOfferID = winnerOfferID;

    tender.TenderOffers.ForEach(o =>
    {
        if (o.ID == winnerOfferID)
        {
            o.Status = TenderOfferStatus.Winner;
        }
        else
        {
            o.Status = TenderOfferStatus.Rejected;
            o.Company = null;
        }
    });
    
    await this._tenderRepository.UpdateTender(tender);
    
    return Ok();
}
catch (Exception ex) 
{
    return StatusCode(500);
}

This is the Update function:

public async Task<Tender> UpdateTender(Tender tender)
{
        if (tender == null || tender.ID <= 0)
            throw new ArgumentNullException("Cannot update, tender is null");
        
    this._context.Tenders.Update(tender);

    await this.SaveChangesAsync();

    return tender;
}

This is the Get function:

public async Task<Tender> GetTender(int id, bool skipCompanyCheck = false, int? companyId = null)
{
    IQueryable<Tender> query = this._context.Tenders.AsNoTracking()
        .Include(t => t.Company).AsNoTracking()
        .Include(t => t.Company).ThenInclude(c => c.Logo).AsNoTracking();

        
    //Other include based on parameters, ALSO TENDER OFFERS
    

    tender = await query.Where(tender => tender.ID == id).FirstOrDefaultAsync();

    return tender;
}